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Discussion Starter #1
Ok, a bit dramatic but it actually sounds like that.

Happens when cold. Started happening within last few weeks but never before.

When cold and driving it to a stop, clutch in and engine drops to idle it seems to drop a little too far and momentarily want to stall. At least thats what I think its doing. The 'growl' is the engine idle just barely getting past where it will run then popping back up on its own. Lasts about as long as the first two warm up lights on the tach then drives normally without idle dropping too far.

Car is all stock except for cat back exhaust, which the car had from previous owner. Spark plugs were replaced when I bought the car (with other things) two years ago august and only 16k miles ago. Air filters also replaced more recently but not coinciding with this change in idle. Stock ECU/no aftermarket tune. No vanos noise now or ever in my ownership.

Car also seems more sluggish when first driven cold than usual.

No SES, but didnt pull codes (as there was no SES). SES light does work, in case you thought to ask, lol.


Did search and only relevant thread I found was this one:
http://www.m5board.com/vbulletin/e3...ing-stop-already-replaced-mafs-fuel-pump.html

In it the following suggestions were made:
-An air leak in the ICV system can cause this stall at idle. Usually when this particular symptom comes up it is one of the orings on the tubes that join the throttle bodies. Part 10 on part 9, that said it could be part 17 also they crack. Remove the plenum and start the car and spray throttle cleaner on the system one piece at a time. When you get close to the leak you will have the rpm come up. When you nail the leak dead on the car will likely stall. Basically you are looking for a change in RPM either way. (Sailor24)

-If the under-plenum vacuum hoses have never been replaced, might be something to consider. Our cars are aging now, so have to factor rubber/plastic part replacement into maintenance. (Caspian65)

-Turn out I had a vacuum leak. Replacing the old, worn, and cracked intake hoses underneath the plenum settled it. I would also check your fuel pump relay to eliminate all other possibilities. (D-RodM5)


Is this the right direction for a fix? Any other diagnostics I should perform? Cam/Crank Position Sensors have not been replaced that I am aware of in recent history, for sure in the 2+ years I've owned it.

Thanks in advance.
 

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Discussion Starter #3
I'll pull codes. No SES though. Never gotten any codes other than the usual secondary air codes. Let me check.
...
 

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Discussion Starter #4
Pulled codes: b3, Catalyst system efficiency, bank 2
No SES, never gotten that code before.

However, recently I also developed too low reading oil and water temps on guage. Could be related to that. I'll post about that separately.
 

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The consensus in your first post was a vacuum leak. Seems reasonable. I think you need to pull the plenum. In the first couple of minutes after start, the DME can't read the O2 sensors so it can't correct for an air leak.

If you have INPA, the fuel adaptations might give a clue.

It won't be the B3 code. That's the DME monitoring the behaviour of the bank 2 cat and deciding it's not working as well as it should. Most times it's caused by AFR problems rather than a bad cat.

I saw your other thread on the oil/water temps but it's a bit inconclusive as to whether you have a problem or not. As a poster suggested, you need to get on the highway and cruise in 6th on a cold day to see if the t/s is sticking open. The secret menu should show KTMP staying at or above 78C.
 

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Discussion Starter #6
I'll run it on highway tomorrow so that should tell me what the temps are and if the tstat is working.
I'll just figure on changing the hoses under the plenum during the holiday break. Yay, more work to do! Volvo xc90 trans flush, new suspension on miata, M work...

Thanks!
 
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