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1 Posts
Discussion Starter · #1 ·
Hey guys,

I have a '97 BMW 740il that is having trouble starting. Backstory: The car sat for a couple months and now it doesn't start. When I got into the car for the first time in months it started fine no problems there and ran for like 5 minutes no problems, funny smells, or weird sounds. After I turned it off it hasn't been able to start successfully for now over 10 sec. The battery, fuel pump, fuel strainer, and fuel filter have all been replaced with no success. The mechanic now thinks its an engine computer(DME) problem but I just have a feeling its not the case. New fuel and injector cleaning fluid have also been tried. For the times that the car does start for like 10 sec. it begins to shake like its struggling with something and then quits. I'm wondering if any one has ever run into this problem before or something similar. I've called around and some other people are saying that it could be an intake manifold gasket problem all the way to the engine mobilizer problem. ANY ADVICE HELPS! Thanks.

E38 - Flight on 4 wheels!
122 Posts
Start with a good diagnostic and save yourself time and $$$. The glitches could be anywhere and especially when you have been sitting for any length of time. These cars need to be active to maintain a certain level of self-preservation and diagnostics. You could potentially have problems in the electrical systems and subsystems, sensors or actual part damage. If you don't know the signs and symptoms you could be troubleshooting a long time with little or no results. If you plan on troubleshooting the whole car, pick an area (engine, suspension, brakes, electrical) and have at it. Finding a reliable indy in your area would be a wise move, trust us, you're going to need a friend, uncle, rabbi, guru, or trusted guy with this car, the sooner the better and more than one is ideal.!

1,271 Posts
If the engine turns , it can't be the car immobilizer, intake manifold gasket can be checked pretty simple with a brake cleaner spray (check for DIY/leak detection video), if the car sat for months I would check the wires under the engine cover and under the engine sometimes rodents like to eat them. I would try to take down the crankshaft sensor and camshaft sensor to clean them and put them back(very common to have sludge deposits on the sensors and they will not read right). And the most important :

Have the fuel pump checked, take it out and look for deposits on the fuel pump absorber. What its happening is : gas has mixture with ethanol. when that stays for months it will corrode your fuel tank and makes tiny rust dust that it will be absorbed with the first key turn. Put you hand at the bottom of the fuel tank and feel for sandy dirt.

Can you hear the fuel pump engaging when you turn the ignition on?

Consider changing spark plugs.

Consider cleaning and greasing with electrical grease fuses and relays.

You may have a valve cover gasket leaking and oil build up down where the spark plugs are.

Try to start it with your MAF disconnected. It may start or not depending on your computer software.

When you run out of options you may blame the DME but you are far away from that. I bet the DME is good.

Good Luck!

766 Posts
I agree with joyism5, in that you need to do more diagnostics to figure out what is causing the problem, and I think the first thing you need to do is to find out if the problem is fuel, or spark.

You should take the fuel line off of the fuel rail, have someone try to start the car, and see if any fuel comes out. If it does, then the fuel system should be working fine, if it doesn't, then the fuel system is at fault.

1 Posts
Sounds like a mass air flow may or may not set a code but you will have to scan it.the diagnostic plug is under the hood on the right side.its round and has a screw off top/cover.with a vacuum leak the vehicle would start unless it was a very major leak and if it was you would hear it.from what you described it attempt to start n advice would be scan it and check the mass air flow sensor.

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Seek to understand,^Value
25,199 Posts
I happened over here in a search ... but in the VERY best of E39 Links you may find this diagnostic thread useful...

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

For example ...

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:

  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. 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 (8)
  • 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.

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)
    • MAF faults often set fuel trim faults (per bimmertec)
    • 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
  • 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 (per bimmertec)
    • Jump 30 & 87 & feel hoses for fuel delivery (1) (8)
      • 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 (per bimmertec)
  • Test the CMP (aka CPS) camshaft position sensor (1)
    • The CMP will set a fault when it is bad (per bimmertec)
    • If bad, replace the CMP
  • Test the CKP (aka CPS) crankshaft position sensor ...
    • If bad, replace the CKP
    • The CKP will set a fault when it is bad (per bimmertec)
    • The CKP often prevents starting (per bimmertec)
  • Test the TPS "throttle position sensor" ...
    • If bad, replace the TPS
  • Test oxygen sensors
    • Best way is to scan them for values (per bimmertec)
    • Pre-cat o2 sensors fail much more than post cat (per oembimmerparts)
  • 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 (per bimmertec)
  • 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)
    • Replace the DISA valve o ring (1) (2) (3)
    • Replace the DISA valve if necessary (1) (2)

  • Check the "valve cover gaskets (VCG)
    • Spray carburetor cleaner on while engine is running (per bimmertec)
    • 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 know what to do (see above)

1 Posts
its a fuel problem,,,air issue ,,mass air flow ,, sounds like its running on cold start injector,,cold inj off,,car dies,,,,=air/fuel....if it was ecu the car would not start then flat wouldn't start.....low voltage to fuelpump? mafs bad connection?? mafs bad? dirty? check voltage?? blow out fuel lines???clogged??
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