My mechanic posted this in another forum can anyone please help??? This has been going on for almost a year now. Any help is greatly appreciated!!

Hey Guys,
Got kind of an odd issue with a 2010 with the N12 and was wondering if anyone else has experienced this issue. I have searched the forums extensively for anyone with a similar issue and have not been able to find anyone with this issue or anything like it. I have exhaustively attempted to repair this issue and to no avail and am look for any input on the matter at this point. The car had been sitting for a few months when we pulled it out of storage at that point it had misfires on various cylinders and a pretty worn out timing chain. I replaced the timing chains and found a few collapsed lifter and due to the fact the vehicle has 150k on it decided to do a head gasket and valve job while i was in there. The only issue i am still chasing that this point is a misfire on cylinder 1 but only once the vehicle is warm (90 degrees C or hotter). Here is the odd part though, if i unplug any of the cam position sensors, vanos solenoids or eccentric shaft sensor the misfire goes away and the vehicle runs great. Also, if i unplug ignition coil 4, the misfire on cylinder 1 goes away if i unplug coil 2 or 3 the misfire on cylinder 1 is still present. Here are the parts ive swapped or replaced.

-Both Vanos Solenoids
-Both Vanos Adjusters
-Both cam postion sensors
-Crank Sensor
-Engine harness
-Coils and plugs
-MAF
-DME
-Eccentric shaft, motor and sensor

In addition i have done both a hot and cold compression and leakdown test which provided good results. I have also updated the vehicle to the latest I-Level. Im running out of ideas on what could be causing this and am hoping someone here has had a similar issue or can point me in a new direction. Thank you!
Reply

 

I would search for a bad ground, bad connection in a connector plug, or maybe a broken wire in the harness. Also could start swapping in known good parts from a donor car.

 

I really appreciate any response. He put in a new engine harness and new ground. Unless we are missing something??? This is so frustrating!

 

Have the adaptations been reset for the ECU, Vanos, etc? Are there any BMW codes? How sure are you that the timing is spot on after the chain replacement? Is the vanos timing in live data within expected limits or is the timing retarded?
I feel your pain, my N12 was idling badly, had misfire after I changed the vanos solenoids and pre cat O2 sensor but it cleared up after adaptations were reset so the ECU could relearn the new parameters.

 

Yes adapations have been cleared probably a couple dozen times as well as the re learn procedures.

Timing can not be off because there are no correlation faults but we did check it mechanically twice.

Vanos operates within its specified range until the misfire happens. Then it pins the vanos and it runs fine.

Code is misfire cylinder 1.

 

We got the car back home. The only way the car will run smoothly is with the O2 sensor disconnected and no Check Engine Light came on for the past 3 days. Once the O2 sensor is connected and the car heats up it starts running rough and has a code of Misfire in Cylinder 1 (no O2 sensor code). Your feedback would be appreciated.

 

Sounds very frustrating. I am sure your mechanic is knowledgeable, and has tried his best but, at this point, I think you need a Mini specialist. Do some research. Try to find an independent, rather than a service tech from a Mini dealer, to avoid being talked into repairs you don’t need. Good luck.

Kat

 

Can you check the engine temp sensor? If ECU thinks engine is cold it won't use O2 sensor (open loop) and it will run rich all the time.
Is idle at spec (not fast)?
Unfortunately temp sensor is part of the thermo housing and I don't think it can be removed separately for testing or replace?

I looked in the manual for temp sensor spec but could not find it. Usually you just put in a pan of hot water at specified temp and check resistance.

Often when a car has misfires and the obvious like spark and fuel issues are ruled out it's a sensor issue such as MAF (you already tried this), temp sensor, O2 sensor etc.
Strange that it's only 1 cyl though but who knows.

Also I know you swapped the MAF but I assume it was also used and a dirty MAF can cause rough running so I would clean it with MAF cleaner - costs you nothing.