OT: problem in e38 740.

[liquidtiger720]

As the title states. My moms new car seems to have a quirk! It was not disclosed to us and the company we bought it from denies it ever happening before. Nor did it happen on the test drive.Anyawys, to the problem. At seemingly random times, after starting the engine, the car would just die...engine stops running , etc etc (basically key in position 2). Today, I had to start it 5 times before it stayed on. (the car was already driven for about 45 min and was already warmed up, stayed off for about 3 hours). So, I have noticed that when it does start up correctly, the rpms jump as usual when it initially fires, but on the way back down to idle, it would climb back up a couple hundred rpm (after hitting idle~600-700 rpm?), and would slowly settle.


Not quite sure what to think of it. Fuel pump/filter? Clogged injectors? Any help would be appreciated. BTW, the 4.4l v8 is quite addicting...especially over my puny 2.5 i6.

[BobHarris]

Dirty throttle body and / or idle control valve?

Bob

[tye1138]

Dirty throttle body and / or idle control valve?

Bob

Idle control valve sounds 100% correct as a place to start.

I'm not too familiar with the v8 motors, but on the M50, M52 motors I've also seen bad electronics for the coil control do the same thing! No spark, no run! I use to have a MODIC and was able to run diag's to figure out the problem. The OBD 1 or 2 software should be able to give you a proper fault when the motor shuts off by itself. If the check engine light goes on, thats a good sign its something the computer is picking up a problem that can be read by a diag tool.

[liquidtiger720]

Actually, the service engine soon light turns on- not the check engine light.

I'll try cleaning the throttle body + icv (if i can find it).

Somebody also suggested the CPS (camshaft position sensor). Could that be another possibility?


thank you for your responses.

[Kalevera]

Hi Josh.

Unlike our cars, the E38 takes two turns of the key after the problem first occured to get the check engine light to flash (if a code has been set).

Unless you have the load speed problem I saw a few months back, a faulty ICV would set a code.

I'd be looking at a fuel pressure or pressure regulation issue. Also, if the power cuts out when the engine turns itself off, it might be a good idea to replace the battery disconnect mechanism.

Hopefully, your mom didn't buy this car with the service lights on; that can only be a harbinger of things to come...

best, whit

[632 Regal]

try to reset the computer with the disconnect method and see if it changes at all, what you describe kinda almost sounds like a vacuum leak which could be anywhere. Also it could be the intake gaskets but they usually give more problems when cold.

I would do the reboot and a close inspection on all the intake tubing and connection spots and hope for the best.