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  #21  
Old 03-12-2023, 09:00 AM
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Quote:
Originally Posted by twarr1 View Post
...After the car starts up and runs horrible for 10-15 seconds it smooths out and idles great. .....
Poor running, that disappears quickly on cold start is often a mixture problem often caused by vacuum leak. Vacuum leak causes intake air to bypass the MAF. After 30 seconds or so the O2 sensors are up to temp and the DME can correct the lean condition by adding more fuel. Check the ST/LT fuel trims using live data w/ODBII scanner.
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  #22  
Old 03-13-2023, 03:42 AM
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Thank you for the reply.
I replaced the eccentric shaft motor seal. It had a small tear in the rubber.
Checked the fuel trims afterwards; Additive - 1.2 and Long term - 0.0.
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  #23  
Old 03-13-2023, 06:56 PM
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That tear creates a vacuum leak. It will cause air to enter the crankcase and intake, bypassing the MAF.
Did replacement fix the rough cold starts?
Fuel trims look good.
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  #24  
Old 03-13-2023, 07:35 PM
ard ard is offline
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Quote:
Originally Posted by pshovest View Post
That tear creates a vacuum leak. It will cause air to enter the crankcase and intake, bypassing the MAF.
Did replacement fix the rough cold starts?
Fuel trims look good.

Vacuum leaks can be an utter BEAR.... unless you are very familiar with the underside of a plenum on the model you have, it can be hard to ID where a cracked fitting or missing hose is or isnt..... (I have a gas S62, for 20 years, so know that well) It doesnt take much to throw the AFR off


Other issue is that the 'size' of the air leak, in relation to the airflow into the engine changes as the RPM goes up. As a result, the DME is chasing the fuel trims around as the engine revs and drops. Decoding the short and long trims can be confusing.

FWIW
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  #25  
Old 03-18-2023, 04:38 PM
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Replacing the eccentric shaft motor seal didnít fix the cold start stumbling issue. In desperation I replaced all 6 injectors and - success! It never recoded a misfire on any particular cylinder so I have to assume all 6 were just worn excessively and leaking.
In this fiasco I replaced;

Spark plugs
MAF sensor
Valve cover gasket
Intake and throttle body gaskets
DISA valves
Evap valve
Evap pump and canister
Eccentric shaft motor and seal
Injectors
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  #26  
Old 03-18-2023, 07:25 PM
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Where the injectors ever "tested" with 12 volts jumper ?
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1988 325is (purchased new) sold
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2008 X5 3.0 (new to me)
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  #27  
Old 03-19-2023, 12:00 AM
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Quote:
Originally Posted by 80stech View Post
Where the injectors ever "tested" with 12 volts jumper ?
No
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  #28  
Old 03-19-2023, 12:00 AM
ard ard is offline
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Did you ever find the 'run-unrest' test on ISTA???


for example: https://www.m5board.com/threads/inpa...rest-s.199081/




Glad it was one of the injectors....
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