rough idle at stops

My 2001 325i idles rough at stops and in park. It has progressively gotten worse and even died once today. It doesn't do it all the time, just randomly. I'm new to the site and don't know much about what's what under the hood besides the basics. Any ideas?

Well, you have a LOT of reading to do. Take a look at the WIKI at the top of every page, and then SEARCH 'till your eyes bleed. There really is a LOT of information on rough idle conditions. Good luck.

After your reading adventure, come back and let us know what you found.

Originally Posted by marlin1881

After your reading adventure, come back and let us know what you found.

If a 'rough idle' is the same (to you) as a 'misfire', then this is quick reading:

- 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)
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)
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)
  • 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
• 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:
-

Could be a lot of things. When it happened to my ZHP it just ended up being a dirty MAF. It could also be a camshaft position sensor, a vacuum leak, VANOS, and probably a few other things that aren't coming to my mind right now

id clean MAF and ICV. quick and easy and may fix, if not, oh well you wasted, what....20 mins? but youd have clean parts and have narrowed things down...just saying

My guess: vac leak

My car did the same and it was a misfire. Go to autozone and they will plug into the computer and give u all the codes for free and it will tell u if you have a cylinder misfiring. Which if it is its probably a coil or a spark plug both easy fixes Do It Yourself and save money.

Originally Posted by checho

Go to autozone and they will plug into the computer and give u all the codes for free.

Just for the record ... that won't work in all states as some make it illegal for Autozone to do the free check...
- Where it's illegal for auto parts stores to lend you an OBDII scanner for free (1) (2)

But, luckily, a decent scanner is only $22 ...
- Where to get the cheapest reasonable ODII scanner in the world (1) (2)

Hi thebob38,

I had this same problem. I had a huge tear in the air intake hose (upper boot). The rubber gets old and dry over time and can develop cracks. A crack in the hose causes rough idling to the point of stalling. Replace the upper and lower boot (the lower one is very hard to remove because of the position of the hose clamp screw).

While your at it. take out your ICV ( Idle Controller Valve) and clean it with carb and throttle cleaner, easy if you can take off the lower boot first.

Also Clean your MAF which is connected to the upper boot air intake hose. Once you do this your car should idle much better.

Once your car is idling better but not perfect you can replace the idle pulley and perhaps replace the belt while your in there. All these things are cheap to do.

Wishing you success in solving your idling problem.

I found a thread from 2010 on this forum; a person had rough idling and cleaned his intake vanos solenoid which he said is simple to do. Afterward he had a nice smooth idle with no stumbling. posted 3-27 2010 by brentboshart - "Rough Idle when cold solved"

My idling after I replaced the air intake hose was much better but not as smooth as it was before I began all my maintenance work. I replaced the oil filter housing gasket which ment taking of the fan, belt, idler pulley, alternator and finally the housing plate. Then putting it all back when the gasket was replaced -*Whew*. When I did all that I had the idling problem and the SES light came on. Ah well.

Through it all I have learned alot about the car and am fairly confidence I'll get my car back in excellent condition. It is after all an eight year old car and parts need to be cleaned and replaced. I live in an area that heavy with pollen in the air, when I open the hood for the first time in many months I was astounded at how dirty it was. Pollen was in every nook and cranny.

I've got to get a flexible screw driver so that I can replace that lower air intake hose (the screw is so hard to get to) - I want to clean the Idler control valve (ICV) was had taken off the DISA box and wonder if I should clean the paddle connected to it. It was coated with oil. But I put it back the way it was. I only wanted to deal with one issue at a time.