General diagnostic procedure for a single or multi-cylinder E39 intermittent misfire?

As our beloved E39s get older, more misfire threads seem to appear, where "replace this" or "replace that" is thrown out as the solution.

Rather than just throw parts at the problem, let's compile a DIAGNOSTIC procedure for debugging WHICH parts to replace to resolve the misfire.

As is my bent, I'll embarrass myself (in the next post) by creating a framework E39-misfire-diagnostic summary for others to correct. This summary will be based mostly on three of the roughly 150 posts in this intermittent cold-start single-cylinder misfire thread; so the summary needs to be fleshed out to be of general use for:

- Single-cylinder misfire diagnostic procedure (intermittent or constant, cold-start or warm)
- Multi-cylinder misfire diagnostic procedure (intermittent or constant, cold-start or warm)

PLEASE IMPROVE SO ALL BENEFIT FROM THE EFFORT!

In my case, this was the presumptive misfire scenario:
A) Misfire occurs more than once/200 revolutions in one cylinder, so that DME cuts off fuel for that cylinder's nearby injector;

B) A DTC diagnostic trouble code is thrown indicating the cylinder that misfired and that the fuel was subsequently cut off & the SES service engine soon light comes on solid yellow (not blinking) to warn the driver;

C) Even if the misfire no longer occurs, the fuel cutoff is only corrected upon the next ignition cycle (or clearing of the DTC with a diagnostic tool if, for some reason, the vehicle is kept running).

D) The SES remains lit for about 50 miles and 3 starts; but the DTC should remain stored for longer than that (how long?).

And, here's what lild said to look for
1--bad fuel
2==trash or gunk in fuel
3---spark plug valve cover seals
4---head gasket leak, or cracked block
5---bad spark plugs
6==bad coil pack or boot (Bentley says to diagnose with an oscilloscope)
7---bad 02 sensors
8---bad maf mass air flow sensor or meter
9---bad fuel injector
10---cracked ring
11---cam shaft sensor cps
12==crank sensor cps
13---bad ground wires
14--- bad fuse or relay
15---bad electrical wiring
16--- dme, or ecu (Digitial Motor Electronics, i.e., the engine computer)
17--intake manifold gasket leak
18--ccv--aka pcv, crankcase oil separation valve
19--icv--idle control valve
20--tps==throttle position sensor
21-- bad VANOS seals (actually poolman added this one)

Here's the algorithm I gleaned from reading everything I could in bimmerfest on the topic (before the above two summaries were made):
0. When you notice a BMW cold-start stumble ...
1. Shut the ignition off & wait 30 seconds before restarting
2. The stumble may go away but look for the SES light on the cluster which should remain
3. If you see an SES, check for a P1349 code and reset the MIL
4. If you have a P1349 code, swap ignition coils between #3 & #4
5. If the intermittent start stumble moves to cylinder #3, replace the coilpoolman coil recall information here)
6. If the start stumble returns on cylinder #4, swap or replace the plug
7. If the stumble returns on cylinder #4, swap or replace the plug boots
-----< after this point, I think we're moving away from the specific cylinder >-----
8. If it returns on cylinder #4, clean the MAF (hot film air-mass meter) with CRC & replace the air filter
9. If it returns, replace the "cam position sensor" (is there one specific to cylinder #4?)
10. If it returns, replace the Cam Position Sensor CPS (is this specific to cylinder #4?)
11. If it returns, replace the post-cat oxygen sensor (the pre-cat 02 sensor is not implicated)
12. If it returns, replace the VANOS seals (can variable valve timing affect only a single cylinder?)
-----< after this point, we're really shooting in the dark >-----
13. If it returns, replace the CCV (aka CVV oil separator valve)
14. If it returns, replace the fuel filter (one guy suggested replacing the fuel pump)
15. If it returns, add a bottle of Seafoam or Techron concentrate to the fuel
16. If it returns, clean the ICV (idle control valve) with carb cleaner
-----< people really suggested all these items in the respective threads
17. If it returns, replace the hose from the MAF to the engine
18. If it returns, replace any cracked "T-connection after the MAF sensor"
19. If it returns, replace the "valve cover gaskets (VCG) into the spark wells"
20. If it returns, clean or replace all the fuel injectors
21. If it returns, replace the "coolant temperature sensor"
22. If it returns, replace the alternator to raise the voltage (yes, this has been suggested)
-----< ok, these were listed as solutions but they aren't feasible >-----
23. If it returns, move to Georgia (from Michigan
24. If it returns, drive the car every day (don't let it sit for two days)
25. If it returns, check the "intake boot" for cracks and replace if necessary
26. If it returns, replace the "throttle position sensor" (TPS)
Note: Don't laugh; I've read dozens of threads and each of these has been posited as the "solution" to this intermittent problem!

Here's my attempt at GENERALIZING that procedure for use by others.

BACKGROUND:
A) If a misfire occurs more than once in 200 revolutions in any one cylinder, the engine computer (DME) cuts off fuel for that cylinder's nearby injector in order to protect the emissions system;

B) A DTC diagnostic trouble code is thrown indicating the cylinder(s) that misfired and that the fuel was subsequently cut off & the SES service engine soon malfunction indicator light (MIL) comes on solid yellow (not blinking if it's only once in 200 revolutions) to warn the driver of the problem;

C) Even if the misfire no longer occurs, the fuel cutoff is "permanent" in that it is only corrected upon the next ignition cycle (or by manual clearing of the DTC with a diagnostic tool if, for some reason, the vehicle is kept running).

D) The SES remains lit for about 50 miles and 3 starts; but the DTC should remain stored for longer than that (how long?).

Theoretically, if an engine isn't running, it's ALWAYS one of the following requirements:
a) Gas, b) Air, c) Spark, d) Timing, e) Compression

More specifically, a precise fuel:air ratio must be ignited at the right time with enough compression to explode. So, all misfires, somehow relate to one or more of those five fundamentals being skewed.

Specifically, here's what to look for (somewhat in this order based on an anecdotal survey of misfire threads):

1. bad fuel [air:fuel ratio]
2. clogged fuel filter [air:fuel ratio]
3. bad fuel pump [air:fuel ratio]
4. clogged engine air filter [air:fuel ratio]
5. vacuum leaks in hoses [air:fuel ratio]
6. bad coil packs [spark]
7. bad coil boots [spark]
8. bad or ill fitting spark plug valve cover seals [spark]
9. worn or fouled spark plugs [spark]
10. bad mass air flow (MAF) sensor or meter [air:fuel ratio]
11. bad DISA valve flap [air:fuel ratio] (1)
12. bad DISA valve o-ring [air:fuel ratio] (1)
13. worn fuel injector seals (o-rings) (1) (2)
14. bad fuel injectors [air:fuel ratio]
15. bad 02 oxygen sensors [air:fuel ratio]
16. cracked rings [compression]
17. bad camshaft position sensor CMP, aka CPS [spark? timing?]
18. bad crankshaft position sensor CKP, aka CPS [spark? timing?]
19. bad ground wires [spark]
20. bad fuse or relay [gas, spark, timing]
21. bad electrical wiring [gas, spark, timing]
22. bad engine computer DME, aka ECU [spark]
23. intake manifold gasket leak [compression, air:fuel ratio]
24. bad crankcase oil separator valve CCV, aka PCV [air:fuel ratio]
25. bad idle control valve ICV [air:fuel ratio]
26. bad throttle position sensor TPS [air:fuel ratio]
27. bad VANOS seals [compression, air:fuel ratio]
28. head gasket leak, or a cracked block [compression, air:fuel ratio]

However, that list above is NOT a debugging algorithm!

What we need is an E39 engine misfire debugging algorithm (here's a start):
When you notice a BMW E39 engine stumble ... it's always either gas, air, spark, compression, or timing; so concentrate on factors that affect those 5 requirements!

• If you're misfiring, immediately shut off the ignition
• Wait 30 seconds before restarting the engine (this resets emissions-related fuel cutoffs)
• Note the presence or absence of a yellow solid or blinking SES light
• Scan for diagnostic trouble codes (DTCs)
  • Write down and DTC and Google that DTC for hints
  • Clear all stored DTCs to see if they return in time
• Reset engine electronics by disconnecting the battery & crossing the cables (with a wrench) for 10 minutes (1)
• Fill your fuel tank with gasoline from a different gasoline station

If you have a specific-cylinder misfire code:

• Swap ignition coils between adjacent cylinders (8)
  • If the misfire moves, replace the bad coil) ...
• Swap spark plugs between adjacent cylinders.
  • If the misfire moves, replace the spark plugs
• Swap the spark plug boots between adjacent cylinders
  • If the misfire moves, replace the spark plugs
• Swap the fuel injectors between adjacent cylinders
  • If the misfire moves, clean or replace the fuel injectors
  • Replace the fuel-injector seals (aka o-rings) (1)
• Check compression differences between cylinders (1)
  • If the misfire cylinder is lower than the rest, squirt heavy duty oil in the cylinder to check the rings

At this point, we're no longer dealing with specific cylinder misfires.
Now we start handling specific component tests, repairs, & replacements:

• Temporarily remove the engine air filter
  • If the stumbling problem disappears, replace the engine air filter
• Temporarily disconnect the MAF & drive the vehicle (1)
  • If the misfire changes, clean the MAF (replace if necessary)
• Clean the MAF & check the hose from the MAF to the engine for leaks
  • If bad, replace the MAF (an overly rich mixture dirties the ICV)
• Check for a cracked "T-connection after the MAF sensor"
  • If bad, replace the T connection
• Test the fuel pump by jumping 30 & 87 & feeling hoses for fuel delivery (1) (8)
  • If bad, replace the fuel pump
• Clean (or replace) the mass air flow sensor (1)
  • An overly rich fuel:air ratio can cause the ICV to stick (1)
  • A sticking ICV can lay a coat of soot on the O2 sensors (1)
• Check for vacuum leaks
  • Run the "intake manifold vacuum leak test" (1)
  • Visually inspect all vacuum hoses
    • If any are bad, replace
    • Cracked CCV hose vacuum leaks often affect cylinders 1, 2, & 3 (1)
• Test or clean the CCV (aka CVV oil separator valve) and its hoses (1)
  • If bad, replace the CCV
• Test the CMP (aka CPS) camshaft position sensor (1)
  • If bad, replace the CMP
• Test the CKP (aka CPS) crankshaft position sensor ...
  • If bad, replace the CKP
• Test the TPS "throttle position sensor" ...
  • If bad, replace the TPS
• Test the I6 VANOS seals (by disconnecting the harness connector)
  • It's not a bad idea to replace the I6 VANOS seals anyway
• Test fuel delivery pressure
  • If low, replace the fuel filter
• Clean the MAF and check the hose from the MAF to the engine for leaks or tears
  • If bad, replace the MAF (an overly rich mixture dirties the ICV)
• Check for a cracked "T-connection after the MAF sensor"
  • If bad, replace
• Check the "valve cover gaskets (VCG)
  • If bad, replace
• Check the "intake boot" for cracks
  • If bad, replace
• In addition to pious pleas to the Lord Jesus, go ahead, add a bottle of Seafoam or Techron concentrate to the fuel

Here is a video testing for vacuum leaks by spraying carburetor cleaner on hoses:

Some of the open questions that remain to be answered are:

For completeness & accuracy:
Q: What else is missing from the sum total of suspected parts?
Q: What needs to be fixed in the flow chart diagnostic procedure?

And ... for diagnostic purposes:
Q: How do you test the CMP (cam shaft position sensor)?
Q: How do you test the CKP (crank shaft position sensor)?
Q: Is there a test for the post-cat oxygen sensor?
Q: How do you test the fuel system delivery?
Q: How do you test the ICV (idle control valve)?
Q: How do you test the VCG (valve cover gasket)?
Q: How do you test the TPS (throttle position sensor)?

Over here, a misfire turned out to be a bad DISA valve.

Here's what the OP had to say:
"Removed the DISA valve. BMW calls it 'adjuster unit', also have seen it called 'manifold adjuster'. The plastic hinge pin was broken on mine, so the flap was just hanging there inside the intake manifold! What a poorly designed piece of garbage. Apparently, the flap remains closed, restricting air intake, until higher RPM's, then it opens to allow more air flow. The valve is not variable, and is either all the way open or all the way closed. Mine was hanging open - running lean. I was very lucky no parts had flown off YET.
Replaced the valve (BMW - $220), problem solved - car runs great and no more codes!"

Originally Posted by bluebee

Some of the open questions that remain to be answered are:

And ... for diagnostic purposes:
Q: How do you test the CMP (cam shaft position sensor)?
Q: How do you test the CKP (crank shaft position sensor)?
Q: Is there a test for the post-cat oxygen sensor?
Q: How do you test the fuel system delivery?
Q: How do you test the ICV (idle control valve)?
Q: How do you test the VCG (valve cover gasket)?
Q: How do you test the TPS (throttle position sensor)?

The post-cat test would be similar to the pre-cat. The Bentley covers the fuel system delivery question. My Snap-On meter can provide the procedures for all the others (except the VCG). I can look these up and report back. The only possible problem is that the procedures may vary by model, engine and year. I'll look into it and let you know if it will be a long list.

Wow, looks like you put a lot of time into this. Thanks! I have the morning stumble in cold weather, and the occasional SES. This will come in quite handy for me.

Bluebee, thanks for doing this! I have a misfire on our 03 540 that i am currently dealing with. SES first pointed to O2 which I replaced, then it pointed to #3 cylinder misfire AND multi cylinder misfire. I cleaned MAF, replaced all plugs and cylinder #3 coil/boot, car runs "better" but misfire still happens when "I put my foot into it"; I cleared the code and it has since stayed off but the misfire still occurs. I think my next step will be to replace the remaining coils unless anyone has another suggestion ????????

BTW - will a failing Camshaft Position Sensor throw a code ?

Originally Posted by TDS

will a failing Camshaft Position Sensor throw a code ?

Notice this description from this excellent canonical thread about the CPS when it comes to failure modes ...

"M52TU engines (99-00) were the first with this vanos. They experience the cold weather cold start ideal jolt symptom, which is quite aggravating. This symptom was patched up in the M54 and M56 software.

So, M52TU cars have the most aggravated owners due to the cold morning symptom, but the M54 & M56 engine cars are also experiencing the vanos failure. They will experience a loss of torque and power, particularly in the lower RPM range (< 3K). They might also experience the lower RPM engine hesitations and hiccups.

As you know, owners are also now starting to experience engine fault codes. The fault codes are all related to the vanos exhaust side. The vanos exhaust side cylinder has a powerful spring inserted in it. The spring advances the piston by default to cause advanced exhaust valve timing. This assures no overlap in intake and exhaust valve opening at startup, allowing for a smooth startup. It takes significant oil pressure to oppose the spring and retard the piston. Due to failing (leaking) piston seals the DME becomes unable to retard the exhaust piston.

This scenario manifests in the following vanos exhaust side fault codes:
P1520 (BMW 104, 0x68): B (exhaust) Camshaft Position Actuator (faulty reference value).

P1523 (BMW 106, 0x6A): B (exhaust) Camshaft Position Actuator Tight or Jammed (mechanically stuck).

P1397 (BMW 18, 0x12): Camshaft Position Sensor B (exhaust) Circuit.
The Camshaft Position Sensor (CPS) is a common failure.

But if replacing the exhaust CPS (w/ OEM CPS) doesn't work then it's likely the vanos failure . "

In addition, this is pertinent to misfires:"What are the symptoms of a failing vanos?
On autos with the M52TU engine (98/99-00) the failing vanos is causing engine idle jolts (dramatic drops) and possibly a stall on cold engine starts (< 55 F / 13 C).
On other cars with the M52TU, M54, M56 engines, car performance will be degraded. The engine will bog and hiccup at lower RPM's (< 3k). There will also be a general loss of torque and power, mostly at lower RPM's (< 3k).

How can I verify my vanos is failing?
On M52TU engine autos (98/99-00) experiencing the cold engine idle jolts, the vanos intake solenoid (metal cylinder) electrical connector can be disconnected. If the idle jolts cease then the problem is most likely the vanos."

The point of this thread is to contain ALL the commonly asked misfire diagnostic questions!

The question came up today about the numbering of cylinders.

V8 M62, M62TU, Firing order... 1-5-4-8-6-3-7-2

• Rear of engine
  • 4-------------8
  • 3-------------7
  • 2-------------6
  • 1-------------5
• Front of engine

i6, M52, M52TU, M54, Firing order... 1-5-3-6-2-4

• Rear of engine
  • 6--------------
  • 5--------------
  • 4--------------
  • 3--------------
  • 2--------------
  • 1--------------
• Front of engine

I am so thankful for all the help this forum has provided. Without it, I might have given up too soon & not been able to fully appreciate this cool car!

I bought my 540i6 from someone who didn't keep any records. He didn't seem to be very mechanically inclined either. He was mostly interested in vanity - he was quick to point out all the cosmetic things he had replaced (cup holders & etc). He wasn't interested in keeping up with the maint. paperwork either.

I had a misfire, and without any documentation, here is what I did towards this problem.

I needed to establish a 'stick in the sand' so I could have a known base line. I did this by buying a code reader & after reading the codes, I cleared them & performed the most basic of tune ups (replaced the valve cover gaskets, spark plugs, plug boot & coils). I still had a misfire & since I had rulled out the coils & spark plugs, I checked for vacuum leaks (none) & I checked the MAF & other intake parts (all clean & looked good/ new).

In the process of this work, I found lots of evidence that led me to believe this has been a recurring issue with this car. I decided to proceed with the assumption that all the obvious items had already been checked or replaced. This led me to think about the process a bit more. Since it idled very smooth & ran well under high intake vacuum conditions, I was looking for causes under higher loads. All I could come up with was poor electrical signal transmission to the injectors & coils. I decided to start at the injector connections. After wiggling the fuel injector elec connector on the offending cylinder, the misfire went away.

Sometimes, we overlook the most basic things. However, after 13 years, the electrical connectors may have just enough oxidation to create an erratic connection.
My plan is to clean all the connectors when the car is down waiting for the pixel repair. In the mean time, I'm driving her every chance I get.

It's awhole lot easier than that you just need a scanner. If thers a fault for your cam senors, ther the problem, if your mass air flow is at fault you will also have fuel trim faults same as a clogged fuel filter. if you have a single cylinder misfire, swap the plug to another cylinder and swap the coil to a seperate cylinder i.e. misfire cylinder 3 swap the plug with the one from cylinder 1 and the coil with cyl 2. if the fault follows one of them thers ur problem if it stays its your inkector. if you have mutiple misfire and lean faults stored most likely you need and fuel filter or its your crankcase vent valve. Mass air flow sensors rarely set misfire faults they will set fuel trim faults and also may set a fault for the icv

also alittle trick iv learned from my experiance working on these cars, If you have a m54 that runs fine but when the coolant guage gets to the top of the blue during warm up and starts to misfire real bad and may even stahl but then goes away as it warms up and sets mutiple misfire faults your vanos unit is faulty even tho it dosent set a vanos fault

Originally Posted by bluebee

Some of the open questions that remain to be answered are:

For completeness & accuracy:
Q: What else is missing from the sum total of suspected parts?
Q: What needs to be fixed in the flow chart diagnostic procedure?

And ... for diagnostic purposes:
Q: How do you test the CMP (cam shaft position sensor)?
Q: How do you test the CKP (crank shaft position sensor)?
Q: Is there a test for the post-cat oxygen sensor?
Q: How do you test the fuel system delivery?
Q: How do you test the ICV (idle control valve)?
Q: How do you test the VCG (valve cover gasket)?
Q: How do you test the TPS (throttle position sensor)?

the cam position sensor will set a fault so you know its bad. the crank sensor will set a fault and 9 times out of 10 the car won't start. the best way to test a pot cat o2 sensor is to read it with a scanner if it moves around or reads anything other than lean it or your cat is bad. to test the fuel delivery system you need a fuel gauge ther is a fitting on the fuel rail. the icv is alittle tough to diagnose but alot of time it will set a fault for the mass air flow sensor and a bad mass air flow can set a fault for the icv. if the vcg is suspect spray carb cleaner around it the idle will jump if thers aleak.

i hope all of this helps

Originally Posted by bimmertec

the cam position sensor ... crank sensor ... o2 sensor ... fuel delivery system ... icv ... vcg ...

Thanks. Together we can build a great BMW E39 tribal knowledge misfire-detection algorithm!

I added it all below after doing a recopy of the BMW E39 misfire-detection & resolution algorithm from post #3 above (because I can no longer edit that post), and continuing below.

- How to diagnose a BMW E39 engine misfire (1)

BMW E39 engine misfiring is ALWAYS due to one of the following:

• gas
• air
• spark
• compression
• timing

Tribal summary on BMW E39 specific misfire culpability: (after reading hundreds of E39 misfire threads and manually collating the results)

1. bad fuel [air:fuel ratio]
2. clogged fuel filter [air:fuel ratio]
3. bad fuel pump [air:fuel ratio]
4. clogged engine air filter [air:fuel ratio]
5. vacuum leaks in hoses [air:fuel ratio]
6. bad coil packs [spark]
7. bad coil boots [spark]
8. bad or ill fitting spark plug valve cover seals [spark]
9. worn or fouled spark plugs [spark]
10. bad mass air flow (MAF) sensor or meter [air:fuel ratio]
11. bad DISA valve flap [air:fuel ratio] (1) (2)
12. bad DISA valve o-ring [air:fuel ratio] (1) (2) (3)
13. worn fuel injector seals (o-rings) (1) (2)
14. bad fuel injectors [air:fuel ratio]
15. bad 02 oxygen sensors [air:fuel ratio]
16. cracked rings [compression]
17. bad camshaft position sensor CMP, aka CPS [spark? timing?]
18. bad crankshaft position sensor CKP, aka CPS [spark? timing?]
19. bad ground wires [spark]
20. bad fuse or relay [gas, spark, timing]
21. bad electrical wiring [gas, spark, timing]
22. bad engine computer DME, aka ECU [spark]
23. intake manifold gasket leak [compression, air:fuel ratio]
24. bad crankcase oil separator valve CCV, aka PCV [air:fuel ratio]
25. bad idle control valve ICV [air:fuel ratio]
26. bad throttle position sensor TPS [air:fuel ratio]
27. bad VANOS seals [compression, air:fuel ratio]
28. valve cover gasket (VCG) leak [air:fuel ratio]
29. head gasket leak, or a cracked block [compression, air:fuel ratio]

BMW E39 tribal knowledge misfire-troubleshooting algorithm:

• If your engine is misfiring, immediately turn off the ignition
• Wait 30 seconds before restarting the engine (this reputedly resets emissions-related fuel cutoffs)
• Note the presence or absence of a yellow solid or blinking SES light
• Scan for diagnostic trouble codes, aka DTCs (1) (2) (3) (4) (5) (6)
  • Write down any "stored" DTCs & do a search for hints (1) (2)
  • Write down "pending" DTCs & do a search for hints
  • Clear all stored & pending DTCs to see if they return in time
• Reset engine electronics by disconnecting the battery & crossing the cables (with a wrench) for 10 minutes (1)
• Fill your fuel tank with gasoline from a different gasoline station

If you have a specific-cylinder misfire code:

• Swap ignition coils between adjacent cylinders (1)
  • If the misfire moves, replace the bad coil) ...
• Swap spark plugs between adjacent cylinders.
  • If the misfire moves, replace the spark plugs
• Swap the spark plug boots between adjacent cylinders
  • If the misfire moves, replace the spark plug boots
• Swap the fuel injectors between adjacent cylinders
  • If the misfire moves, clean or replace the fuel injectors
  • Replace the fuel-injector seals (aka o-rings) (1)
• Check compression differences between cylinders (1)
  • If the misfire cylinder is lower than the rest, squirt heavy duty oil in the cylinder to check the rings

At this point, we're no longer dealing with specific cylinder misfires.

Multi-cylinder system & specific component tests:

• Test the engine air filter
  • Temporarily remove the engine air filter
  • If the stumbling disappears, replace the engine air filter
• Test the Mass Air Flow meter (MAF) (1)
  • MAF faults often set fuel trim faults (1)
  • Temporarily disconnect the MAF & drive the vehicle (1)
    • If the misfire changes, clean the MAF (1)
    • Replace the MAF if necessary
• Check the hose from the MAF to the engine for leaks
  • If bad, replace the MAF (an overly rich mixture dirties the ICV)
• Check for a cracked "T-connection after the MAF sensor"
  • If bad, replace the T connection
• Test the idle control valve (ICV)
  • An overly rich fuel:air ratio can cause the ICV to stick (1)
  • A sticking ICV can lay a coat of soot on the O2 sensors (1)

• Test the fuel pump
  • Connect a pressure meter to the fuel delivery rail (1)
  • Jump 30 & 87 & feel hoses for fuel delivery (1) (2)
    • If bad, replace the fuel pump
• Check for vacuum leaks
  • Run the "intake manifold vacuum leak test" (1)
  • Visually inspect all vacuum hoses
    • If any are bad, replace
    • Cracked CCV hose vacuum leaks often affect cylinders 1, 2, & 3 (1)
• Test or clean the CCV (aka CVV oil separator valve) and its hoses (1)
  • If bad, replace the CCV
  • CCV faults often set fuel trim faults (1)
• Test the CMP (confusingly aka CPS) camshaft position sensor (1) (2)
  • The CMP will set a fault when it is bad (1)
  • If bad, replace the CMP
• Test the CKP (confusingly aka CPS) crankshaft position sensor ... (1)
  • If bad, replace the CKP
  • The CKP will set a fault when it is bad (1)
  • The CKP often prevents starting (1)
• Test the TPS "throttle position sensor" ...
  • If bad, replace the TPS
• Test oxygen sensors (1)
  • Best way is to scan them for values (1)
  • Pre-cat o2 sensors fail much more than post cat (1)
• Test the I6 VANOS seals (by disconnecting the harness connector)
  • It's not a bad idea to replace the I6 VANOS seals anyway
• Test fuel delivery pressure
  • If low, test and/or replace the fuel filter
  • A clogged fuel filter often set fuel trim faults (1)
• Check the DISA valve for midrange operation
  • Remove DISA valve and check plastic flap for operation (0) (1) (2) (3) (4) (5) (6) (7) (8) (9)
  • Replace the DISA valve o ring (1) (2) (3)
  • Replace the DISA valve if necessary (1) (2) (3)

• Check the "valve cover gaskets (VCG)
  • Spray carburetor cleaner on while engine is running (1)
  • If idle improves, replace VCG
• Check the "intake boot" for cracks
  • If bad, replace
• Just before you get down on your knees for pious pleas to the Lord Jesus, go ahead, add a bottle of Seafoam or Techron concentrate to the fuel & see if that improves the misfire.
• If you get this far, and you still haven't located or resolved your misfire, you actually now have a bona-fide 'new' problem that has not yet been seen in the Bimmerfest E39 forums!
  • If you got this far, then open a misfire thread on Bimmerfest!

Please, everyone: As we diagnose future misfires, let's add value to this tribal knowledge misfire diagnostic tree so that all benefit from every action!

Hi folks,

thank you for this excellent thread on the 6-cylinder-misfire thing. Although many people seem to experience this problem, there is only litte to be found on the web about it that makes sense.

I want to add something, though:
After I bought my BMW 6 months ago, it was not running very well, only on 5 cylinders most of the time.
My BMW had the following error codes: Misfires on Cyl. 4, Cylinder cut-off due to misfires, Lambda values out of mearuement range, fuel injection at maximum range, intake cam shaft sensor broken.

I first replaced the camshaft sensor and all the hoses of the crank shaft housing valve and the valve itself. The lambda, fuel injection and cam shaft sensor errors were solved, the misfire (though without the cut-off of the cylinder no. 4) persisted.

I replaced many parts, like ignition coils and plugs, spark plugs, wiring from DME to ignition coils and some faulty temperature sensors. I cross-changed ignition coils, injectors and so on. I cleaned the injectors in an ultra sonic cleaner. I checked the cam shafts for abnormal pitting or wear.

Before opening the engine itself, I wanted to make sure there is no other, cheaper source for the misfire. So I found myself a company that checks and repairs DME-units. And guess what, they told me that the circuit/amplifier/mosfet is broken that does control the injector of cylinder 4....unfortunately, repairing it will cost about 600 $ :-/

So, if the misfire is only on one cylinder and does not move to another one when cross-changing parts between cylinders, make sure you find someone to check your DME.

I read about so many people replacing their hydros (are the called like that) or worse for 1000s of dollars with no effect...better make sure the DME is working properly.

Best regards

Oliver aka Tomcat0815

a member a while back posted a downloadable bentley, i belive the first version. if you can find that, it could help people to test any sensor they want to test, and all can be tested including the fuel pump, relays, etc...

a vcg is hard to test, usuall when they go bad, one of or both will happen. oil will leak down the side of the motor, and will burn off the exuasht, the other is it will leak into the cylinders. and if that happens and you get a specific misfire, when you take the plugs out, it should be a dead give away. as matter of fact if you can it, a lot of manuals have pics. of worn out plugs and what should cause them to mess up.

also one part that could play a factor is a air temp sensor, not the one that gives you the outside temp but the one located in the air intake manifold. it monitors the temp of the air in the intake. but that rarely goes bad.

also a disa valve were added after 8/98, so the early e39 don't have them. and folks who have a k&n can over oil them on the reclean, and the extra oil can mess up the maf, so the maf may not be bad.

you also have engine temp sensor, that monitors the temp of the motor, you have two one that goes to the guage and on to the ecu.
and a leaking head gasket can do the trick too. a compression test is the only way to find out.

LATEST UPDATE:

- How to diagnose a BMW E39 engine misfire (1)

BMW E39 engine misfiring is ALWAYS due to one of the following:

• gas
• air
• spark
• compression
• timing

Tribal summary on BMW E39 specific misfire culpability: (after reading hundreds of E39 misfire threads and manually collating the results)

1. bad fuel [air:fuel ratio]
2. clogged fuel filter [air:fuel ratio]
3. bad fuel pump [air:fuel ratio]
4. clogged engine air filter [air:fuel ratio]
5. vacuum leaks in hoses or the air-intake conduits [air:fuel ratio] (1) () (3)
6. bad ignition coil packs [spark] (1)
7. bad ignition coil boots, aka "spark plug socket" [spark] (1)
8. bad or ill fitting spark plug valve cover seals [spark]
9. worn or fouled spark plugs [spark] (0) (1) (2) (3) (4) (5) (6)
10. bad mass air flow (MAF) sensor or meter [air:fuel ratio]
11. bad DISA valve flap [air:fuel ratio] (1) (2)
12. bad DISA valve o-ring [air:fuel ratio] (1) (2) (3) (4)
13. worn fuel injector seals (o-rings) (1) (2)
14. bad fuel injectors [air:fuel ratio]
15. bad 02 oxygen sensors [air:fuel ratio]
16. bad camshaft position sensor CMP, aka CPS [spark? timing?]
17. bad crankshaft position sensor CKP, aka CPS [spark? timing?]
18. bad ground wires [spark]
19. bad fuse or relay [gas, spark, timing]
20. bad electrical wiring [gas, spark, timing]
21. bad engine computer DME, aka ECU [spark]
22. intake manifold gasket leak [compression, air:fuel ratio]
23. bad crankcase oil separator valve CCV, aka PCV [air:fuel ratio]
24. bad idle control valve ICV [air:fuel ratio] (1) (2)
25. bad throttle position sensor TPS [air:fuel ratio]
26. bad throttle body [air:fuel ratio] (1)
27. bad throttle body o-ring seal [air:fuel ratio] (1)
28. bad VANOS seals [compression, air:fuel ratio]
29. collapsed lifters due to lifter-bore scouring [air:fuel ratio] (1)
30. valve cover gasket (VCG) leak [air:fuel ratio]
31. head gasket leak [compression, air:fuel ratio] (1) (2) (3)
32. overheating complications, e.g., cracked heads, warped blocks, cam seizures, contaminated main bearings, coolant-caused hydrolock, & cracked rings, piston, & valve damage (1)

BMW E39 tribal knowledge misfire-troubleshooting algorithm:

• If your engine is misfiring, immediately turn off the ignition
• Wait 30 seconds before restarting the engine (this reputedly resets emissions-related fuel cutoffs)
• Note the presence or absence of a yellow solid or blinking SES light
• Scan for diagnostic trouble codes, aka DTCs (1) (2) (3) (4) (5) (6)
  • Write down any "stored" DTCs & do a search for hints (1) (2)
  • Write down "pending" DTCs & do a search for hints
  • Clear all stored & pending DTCs to see if they return in time
• Reset engine electronics by disconnecting the battery & crossing the cables (with a wrench) for 10 minutes (1)
• Fill your fuel tank with gasoline from a different gasoline station

If you have a specific-cylinder misfire code:

• Swap ignition coils between adjacent cylinders (1)
  • If the misfire moves, replace the bad coil) ...
  • Also check your coil harness ground to the valve covers (1)
  • Note: The E39 coils are bolt-down until 8/02 and flip-switch from 9/02 (1)
• Swap spark plugs between adjacent cylinders.
  • If the misfire moves, replace the spark plugs (0) (1) (2) (3) (4) (5) (6)
• Swap the spark plug boots (aka spark plug sockets) between adjacent cylinders
  • If the misfire moves, replace the spark plug boots
• Swap the fuel injectors between adjacent cylinders
  • If the misfire moves, clean or replace the fuel injectors
  • Replace the fuel-injector seals (aka o-rings) (1)
• Check compression differences between cylinders (1)
  • If the misfire cylinder is lower than the rest, squirt heavy duty oil in the cylinder to check the rings

At this point, we're no longer dealing with specific cylinder misfires.

Multi-cylinder system & specific component tests: (1) (2)

• Test the engine air filter
  • Temporarily remove the engine air filter
  • If the stumbling disappears, replace the engine air filter
• Test the Mass Air Flow meter (MAF) (1) (2)
  • MAF faults often set fuel trim faults (1)
  • Temporarily disconnect the MAF & drive the vehicle (1)
    • If the misfire changes, clean the MAF (1)
    • Replace the MAF if necessary
• Check the hose from the MAF to the engine for leaks
  • If bad, replace the MAF (an overly rich mixture dirties the ICV)
• Check for a cracked "T-connection after the MAF sensor" or in the air-intake housing (1)
  • If bad, replace the T connection
• Test the idle control valve (ICV)
  • An overly rich fuel:air ratio can cause the ICV to stick (1) (2) (3)
  • A sticking ICV can lay a coat of soot on the O2 sensors (1)

• Test the fuel pump
  • Connect a pressure meter to the fuel delivery rail (1)
  • Jump 30 & 87 & feel hoses for fuel delivery (1) (2)
    • If bad, replace the fuel pump
• Check for vacuum leaks
  • Run the "intake manifold vacuum leak test" (1)
  • Visually inspect all vacuum hoses
    • If any are bad, replace
    • Cracked CCV hose vacuum leaks often affect cylinders 1, 2, & 3 (1)
• Test or clean the CCV (aka CVV oil separator valve) and its hoses (1)
  • If bad, replace the CCV
  • CCV faults often set fuel trim faults (1)
• Test the CMP (confusingly aka CPS) camshaft position sensor (1) (2)
  • The CMP will set a fault when it is bad (1)
  • If bad, replace the CMP
• Test the CKP (confusingly aka CPS) crankshaft position sensor ... (1)
  • If bad, replace the CKP
  • The CKP will set a fault when it is bad (1)
  • The CKP often prevents starting (1)
• Test the TPS "throttle position sensor" ...
  • If bad, replace the TPS
• Test oxygen sensors (1)
  • Best way is to scan them for values (1)
  • Pre-cat o2 sensors fail much more than post cat (1)
• Test the I6 VANOS seals (by disconnecting the harness connector)
  • It's not a bad idea to replace the I6 VANOS seals anyway
• Test fuel delivery pressure
  • If low, test and/or replace the fuel filter
  • A clogged fuel filter often set fuel trim faults (1)
• Check the DISA valve for midrange operation
  • Remove DISA valve and check plastic flap for operation (0) (1) (2) (3) (4) (5) (6) (7) (8) (9)
  • Replace the DISA valve o ring (1) (2) (3) (4)
  • Replace the DISA valve if necessary (1) (2) (3)

• Check the "valve cover gaskets (VCG)
  • Spray carburetor cleaner on while engine is running (1)
  • If idle improves, replace VCG
• Check the "intake boot" for cracks
  • If bad, replace
• Check for MAJOR engine problems (usually due to overheating) such as:
  • head gasket leak (1)
  • cracked heads
  • warped blocks
  • cam seizures
  • contaminated main bearings
  • coolant-caused hydrolock
  • And, piston, ring, or valve damage (1)
• If you get this far, and you still haven't located or resolved your misfire, you actually now have a bona-fide 'new' problem that has not yet been seen in the Bimmerfest E39 forums!
  • Open a new thread, saying you have a unique misfire!

DIAGNOSIS VIDEOS:
Here is a misfire-diagnosis video showing the coil swap trick:
-

Here is a video showing the Brakleen vacuum test trick:
-

Instead of starting a new thread I figured I would just ask here to consolidate info. I have multiple cylinder misfires, and fuel trimm additive codes. I suspect a vacuum leak is the culprit. so Id like to have a list of all of the possible places a leak could occur. If anyone with experience diagnosing vacuum leaks could help it would be great.

Have you tried this one?

Originally Posted by bobdmac

Have you tried this one?

I have. With mixed results.



BTW, today a 'propane' way to test for vacuum leaks was proposed:
- E39 (1997 - 2003) > 2003 525IT-Smog Failed

Originally Posted by Jimmys 530i

Check for vacuum leaks. Buy a small propane tank, and run a long hose off the end; open the valve just slightly, and hold the hose over vacuum components one at a time. If your idle changes, you have found your leak.

For vacuum leaks, I proposed this thread to outline ALL E39 vacuum lines:
- Might we be able to list, with pics (realoem diagrams ok) of ALL E39 vacuum lines?

And, while doing some research, I ran into this excellent summary of performance-related problems, from the expert in VANOS, Rajaie himself:
- Subject: Re: BMW E39 528i touring 1999 model auto

• VANOS seals
• ICV vacuum leak
  • Either due to ICV air intake boot or gummed up valve
• CCV vacuum or pressure problems
  • Either due to leaks in hoses or clogs in the CCV hoses
• DISA valve
  • Either due to a broken flap
  • Or due to a leaking o-ring
• MAF sensor
  • Either due to a broken flap (I didn't know my MAF had a flap?)
  • Or due to a fouled sensor
• Fuel filter
  • Usually clogged
• Spark plugs
  • Usually fouled or worn
• Air filter
  • Usually clogged
• Precat oxygen sensors
  • Degrade over time
• Camshaft position sensor (CMP)
  • May fail with or without throwing a code

I tried to print Raj's letter to PDF (Rajaie_explains_BMW_E39_VANOS_related_performance_ issues.pdf) but the PDF has crud splattered on top so I will simply add the text as a referenced quote below.

Originally Posted by Rajaieq

*******>********> The vanos seals are failed on all the cars and replacing them should provide significant performance improvements. But if there is another performance related problem you will not receive the benefits of the new seals until the problem is resolved.
From your description I expect you have a performance related problem in addition to the vanos seals.
Below is a list of the common performance related problems. I would guess you have a vacuum leak. This is usually the idle control valve air intake boot branch or the crankcase vent valve and 4 hoses.

Hope this helps.

The idle control valve air intake boot branch gets cracks in the outer elbow accordion valleys. This can be inspected with a flashlight and mirror.

The idle control valve gets gummed up and sticks. Take it out and clean it with brake cleaner and towels.

The DISA valve is problematic on 01+ cars.
The DISA is a black box 4" high 6" wide on the side of the intake manifold adjacent to the MAF. Remove it. The flap should rotate with resistance and spring back when released. It shouldn't have any play. It breaks at its base axis. If it’s broken, the flap end axis pin can be removed and the flap will fall off.
The 01+ DISA has a base gasket built into the DISA. It shrinks over time and creates a small vacuum leak. Place an 8" piece of electrical tape on a table top. Cut the tape half width with a razor knife. Place one layer of half width electrical tape over the base gasket. This will thicken the gasket and create a tight seal with the intake manifold.

The crankcase vent valve and 4 associate hoses fail and cause a vacuum leak. The valve gets stuck open and the hoses crack. These last 70-120k miles and usually fail 80-90k miles. Here are a couple diagnoses.
At warm idle, place a small plastic freezer storage bag on its side over the oil fill hole. If the bag sits on top or gets slightly sucked in, ~1”, the valve is good. If the bag gets significantly sucked in the hole the valve is stuck open and bad.
With the engine off and cold, carefully remove the hose at the valve cover front corner. Blow hard into the hose. You should hear oil bubbling in the oil pan. If you don’t hear the bubbling the top or bottom hose is likely cracked. The bottom hose often breaks just below the valve connection. There can also be cracks in the other two hoses.

The MAF sensor can be dirty and not perform well or can be failing. After market oiled air filters foul the MAF.
Take out the MAF and clean it with CRC MAF spray cleaner. Spray the MAF lightly. There are delicate wires that can be damaged. Let the MAF fully dry before reconnecting.
Cold air intake setups can drive the MAF beyond its intended operating limits and cause it to fail.
The MAF can be tested by disconnecting its electrical cable connector. If the performance problem resolves it might be the MAF. But this test can be deceiving and should be used with great care. When the MAF is disconnected the DME will err on enriching the air/fuel mix. This can easily cover up another performance problem like a vacuum leak. If the problem is unchanged after disconnecting the MAF the problem is not the MAF.
Aftermarket MAF sensors don’t work.

The fuel filter gets clogged and inhibits the flow of fuel. Replace it every 60-100k miles.

Sparkplugs should be replaced every 60k miles.

Replace air filter every 15k miles.

Pre-cat O2 sensors have a lifespan of 100k miles. They have a significant effect on fuel consumption. They also affect performance. When they start degrading they cause a rich air/fuel mix. This will degrade performance some but will not cause any rough running symptoms. The main symptom is degraded fuel consumption.
The pre-cat O2 sensors are not used on cold weather cold start. The O2 sensors don’t function when cold and are thus not utilized by the DME.
Aftermarket O2 sensors don’t work.

Camshaft position sensors can fail and cause problems. They will usually produce a code, but they might initially malfunction without producing a code. A failing exhaust CPS will cause light performance problems. A failing intake CPS can cause significant performance problems.
Aftermarket CPS sensors don’t work. OEM CPS sensors are only available through BMW. OEM CPS sensors have a BMW logo and this can be used to check if a CPS sensor is OEM.

Rajaie
528i 5sp 06/00

I think Bluebee is a cyborg robot from the future that knows something about the E39s that we dont. It is blues mission to inform us with as much information about the E39 as humanly possible so we can back up all the valuable info that Blue has provided so the internet wont become human and destroy all the information on this site.

Not only is this info helpful for E39s, this is what Im goin to check off through for an E46 thats having issues. Ive already gone through about half the checklist for finding the misfire fault.

Originally Posted by linf94112

Not only is this info helpful for E39s, this is what Im goin to check off through for an E46

Along that vein, I noticed in the E46 forums today a 'rough idle' thread.
- E46 (1999 - 2006) > rough idle at stops

Since I'm not sure whether 'rough idle' equates to 'misfire' in people's minds (it does in mine), I was hesitant to point the user to this thread.

May I ask the general community this question:
Q: Is a BMW E39 "rough idle" the same or different than a "misfire"?

If so, how?