Hello everyone, greetings from a long time lurker. I am hoping that anyone also had my/similar issues or can lead me in the right direction to solve my issue with my R56 N18 Cooper S (180k km). I have INPA & ISTA available.

After having a failed spark plug and coil, I had to drive back home on 3/4 cylinders - replaced all plugs and one coil and then the misery began.

Startup is good but as soon as the coldstart is done the engine runs (on all cylinders) in very rough idle with RPM going up and down in between 600-900RMP until eventually dying. Since no codes are shown (read out with Ista and Inpa) I already checked nearly everything and replaced many(see list below) old/faulty/worn parts - no success.

List of doom:

• Cylinder compressions - ok
• Cylinders inside (endoskop) - ok
• Vanos cleaned (both)
• chain tensioner - replaced
• valve cover - replaced
• intake manifold gaskets - replaced
• inlet/outlet valves - ok , no carbon
• throttle body - replaced
• fuel breather valve - replaced
• All air intake sensors - replaced
• O2 sensor (pre cat) - replaced
• Sensor cooling water - ok
• ambient temperature sensor - ok
• Railpressure - ok
• Reset all adaptations after I replaced all the parts

Any tips/ideas are welcome - since I have none left [img]data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7[/img].

Cheers!

English is not my mother tongue

 

Sounds like you should be looking for an air intake leak or vacuum leak.

What are the short term and long term fuel trims (%) from the upstream O2 sensor when the engine starts running poorly?

 

Hi Maybe - thanks for the reply!

• no air intake leak could be found (tested with smoke and starter spray)
• vacuum leaks could also not be found (so far)

STFT/AFR steadly decrease up from starting the engine until reaching the following values (and rough idle) --> its running way to rich right?

• LTFT: +0,1%
• STFT: -25%!
• AFR: 13,52!

Is there a better way to check for leaks on the vaccum lines other then spraying them with starter spray?
Are there any "hidden" vacuum lines I may have missed to check?

Greetings

 

The upstream O2 sensor is reading an off-the-scale high rich condition. Did you check for a stuck open fuel injector?

What is the MAF sensor reporting for air flow rates at idle?

 

MAF shows 20kg/h at idle and increase with throttle accordingly. Also checked the airfilter - all good.

Good point regarding the injectors - will check tomorrow asap.
I have 2 questions: Would it be „enough“ to run them with carb cleaner while open/close them with an external 9V batterie to check for leaks?
Do I need special tools to either replace them or fit back the old ones after cleaning?

Thanks for the help!

 

This video provides multiple diagnostic ideas. I would recommend starting with the simplest procedures and moving to more advanced and time consuming procedures as necessary.

 

Just a side note: For my 2012 MC N16, the MAF air flow rate at idle is 3.7g/s (~13Kg/h). Not sure if the MAF air flow rate for the N16 should be lower than for the N18.

 

Hi - thanks for the video! Since I could check nearly all the points he mentioned I checked my injector's and oh boi what a mess :D.

Two of them have been leaking so I replacement them all to not have to check them in the near future (hopefully).
I did a reset of all adapdations and after a few misfires they engine runs way better and does not stall anymore but the problem is not 100% gone. (jumping RMP still a bit and stft -19%)

Do you think that this might be due to the ECU needs time to adjust to the changed parts (and adapt accodindgly) since I didn't had the time (yet) to go for a proper testdrive.

Cheers

 

Congrats on the progress!

Definitely do some driving to give DME adequate time to adapt.

 

Thanks! I'm already excided if that's finally it - did only run the engine in idle for like 30sec to check if the fuel-rail is good and if it's holding the pressure after turning off the engine as stated in the video you linked - all perfect!

Before my testdrive however I really need to do an oil change first...just checked it and (prob. due to the leaking injectors) it's over max and smells very stong petrol'ish.

Wish me luck! - I will update this thread as soon as I come back tomorrow.

 

Thanks and good luck! Good thinking on the oil change.

 

Quick update: Wanted to drive to the place where I do my oilchange (~2km) but I had to return after the first 500m due to lack of throttle and misfires.

Observed issues only under load (medium torque): misfirings and very little throttle respsone --> like little crackling when pushing the paddle
In idle I could not observe any misfires, even when reving up to 3-4k.

Do you have ideas what could cause this or any tests I could run do to give more insight?

My next plan is to check for the cylinder 1-4 misfire counters via OBD and to hopefully find a faulty coil.

 

Any fault codes?

 

Still no codes.
Did the oilchange (finally) at my place, put in some fresh NGK iridium spark plugs.
Car still drives like absolute sh**. Still have the rough idle and sputtering when trying to accelerate.

Is there anything left that I might have missed or I can check?

 

Is there any chance that you accidentally mixed up some sensor connectors or fuel injector connectors?

Keep looking for fault codes that may provide helpful clues.

 

Nope - maybe I didn't had only 1 but 2 damaged coils? Since air is fine and fuel also - the last thing would be the coils (since I only changed 1 because it was running on only 3 cylinders).

Or something totaly different - could it be due to a low battery? Mine shows the low power warning at start up, but the startup itself is instant and without any hesitation.

 

Also, maybe you would get some helpful insights by looking at both operational smoothness values and misfire rates for the 4 cylinders.

 

^Can you give more details?

You may want to check whether the serpentine belt is turning the alternator pulley and whether the alternator is able to charge the battery.

What voltage do you read across the two battery posts when engine is off versus when engine is idling?

 

Will check the operational smoothness values and misfire rates for the 4 cylinders in idle and while driving when I come back later.

The battery is kinda low due to short engine run time within the last 6 weeks and OBD diagnostics with engine off but CL15 ON. When I let it idle and/or go for a 1-2min drive the warning stays off for a couple days. I think the battery might need a proper drive to get charged to full.

 

Hook up a battery charger, if you have one, and then verify that battery holds a charge of at least 12.6V overnight.

 

Hi there - since the missfire counters and smoothness values did not show any suspicious data, I did multiple short (1-2min) drives to check the spark plugs after every run and tested with 2 sets of new ones.

The sparkplug of Cyl. 1 always was full of carbon and the other 3 looked pristine. I also switched the plugs around and the ones looking good turned black as soon as I put them in Cylinder 1.

So my conclusion is that I really do have another bad coil. And if its not the coil then it must be the wiring/connector - although I could not find any damage/issue when I checked them.

 

Swap cylinder 1 coil with cylinder 4 coil. Does the black spark plug problem follow the cylinder 1 coil?

 

Heyho - so after some more testing I could figure out that its prob. not an spark-plug/coil issue. I have replaced the remaining old parts with new ones and the issue did not change - It prob. just was a coincidence.

The I remembered that I did NOT check for leaks at the pressure converter and vakuum tank --> Could this even be an issue to make the engine run to rich?
If so is there a way of testing this since I cannot reach it correctly with starter spray?

My suspission gets backed up by hearing a loud hissing after the last cold start - the wastegate and vakuumpump outlet are fine.
What else could have caused the loud hissing? After that hissing the enginge ran rough again...as usual :(

Cheers

 

Since completing the recent fuel injector work, have you rechecked the fuel trims? Is the engine still running rich?

 

Yes, still running to rich even with the new injectors.

So if the vacuum tank or pressure converter (incl. the lines) can’t have an affect on the rich mixture I will bring it to a workshop, since all the mixture involving parts are replaced with new units and I have no idea on what even to check further, that could lead to the rich running.

Does it make sense to let perform a leak down test although compression is 140-145 psi on all cylinders?