[AlpineweissF10]

I've been chasing mixture too rich and misfires on my 2012 PWG N55 and I'm literally stuck as nothing seems to solve the issue. There is a noticeable stumble at idle and it only starts when engine is at operating temps. Additionally misfires are isolated on Cylinders 3 & 4.

Mods:
Chargepipe
Cat**ss downpipe
XHP transmission tune
XDelete


ISTA Screen Shot

**Note: I unplugged the MAF to see if the idle would fix itself triggering the Code 108001.

What I've done so far:
1. Walnut blasting
2. New coils and plugs
3. Replaced leaking PCV valve
4. Removed the BM3 tune back to stock (I've only ran Stage 1 - 91 Octane on the car)
5. Replaced injectors in Cylinders 3 & 4

Short full throttle log: http://www.bootmod3.net/log?id=62e3370dae729b2d5d51d544

Idle log after CEL: http://www.bootmod3.net/log?id=62e3370dd10b432dfabc1fa4

Not sure where else to go from here.

Any help is greatly appreciated.

[BrandBMW]

Compression test?

[Matgsand]

Go for a combustion leakage test or pull plugs 3 and 4 when engine is warm and coolant under pressure - and listen carefully for any hissing noises from those cylinders. Blown head gasket or cracked engine block.

[AlpineweissF10]

Based on the 2 tests, the motor is seems mechanically healthy.

Compression:
1. 209
2. 208
3. 209
4. 210
5. 211
6. 209

Cylinder leakage Test:
1. 2%
2. 2%
3. 3%
4. 2%
5. 1%
6. 4% (in my defense it was very difficult to set TDC from under the car)

I looked at the possibility that it could be O2 sensor related since the rough idle starts when the engine is warm - aka closed loop (lessons from back in my maxima days). Checked values via ISTA and both before and after cat are moving in synch. The multiplicative mixture adaption value is higher at 0.7 (car is running rich)

I then moved to VANOS testing in ISTA. VANOS intake solenoid valve came back with target values that were close to actual however I kept getting an error on the exhaust side, "Timing chain is under tensioned OR timing is nor set correctly".

ISTA called for the following procedures:

1. Check tightening torque of central bolt
2. Check control unit (chain, tensioning pulley etc)
3. Adjust valve timing according to repair instructions as necessary

ISTA also has another set of procedures to check the VANOS exhaust solenoid valve for:

- Stiff movement
- Locking due to dirt contamination (swarf)
- Electrical malfunction

Obviously I'll start with checking the solenoids which is the easiest (probably tomorrow).

[Anwar1995]

Hey Man, I just saw your post regarding the issue. it seems like we are on the same boat. I replaced my valve cover but no avail. the code came back after driving the car for few minutes then stop the engine and stating it again.

I have noticed that my boost solenoid keeps buzzing after the engine is warm and according to the internet that can a location for a vacuum leak. Is your car by any chance making this sort of noise?

Also I am not sure if it is related to the issue but it seems like my post-cat O2 sensor is gone. got a code for it that the voltage is too low and when I checked via the scanner after the car starts it shoots to 1.2v then gradually goes down to 0v.

[AlpineweissF10]

I did notice a buzzing noise and actually thought it was coming from my valve cover. I'm waiting for my vanos solenoids and camshaft sensors to come in so I can put the car together.

Are you planning on replacing boost solenoid? If you do, let me know if it solves your issues.

I'm also thinking of replacing my O2 sensors as more of a preventative measure.

[Anwar1995]

The shop actually had a 335i with the N55 engine which needed some work so they borrowed the boost solenoid from that and tested it in my car. The buzzing noise is definately gone but the issue still ongoing.

I am really starting to think its mostly related to rich mixture overall rather than issues with individual cylinders as I have noticed that the car is running super rich after few shutdowns and startups after its being warm. The long term fuel trim goes to -27% which is super rich (to my humble understanding).

People in the forums are saying that post-cat is only to monitor catalyst efficiency and does not contribute to air/fuel mixture control but I saw one post where a person changed his post-cat O2 sensors and it did actually help his running rich issue so I donno.

Last point is me rambling about my case but I think both of our cases are related to O2 sensors. I saw one thread talking about the lifetime of those sensors and it seems like BMW recommends changing them at around 120k miles as they wear by mileage and my car is currently at 121k.

[Anwar1995]

Hey,

I am not sure if you got your issue sorted but I thought I might give you an update on my issue.

Short answer I think I got the issue fixed and it was the HPFP.

Long answer:

I took the car to a shop specialized in BMWs and MINIs and they diagnosed the car. They told me that there is control valve on the HPFP that seems to be not working properly. Its called "Quantity control valve". Basically from my understanding it regulates the fuel flow going to the HPFP and when it fails the fuel flow is not being controlled proparly thus the rich condition and the misfires.

What they showed me exactly is that you can read how much percentage wise the valve is operating at using a scanner and in my case it was always at 0%. one would think that this would throw a code but it didn't for some reason. Anyhow when they pulled my HPFP it was the orginal one that came with the car with the manufacturing date of 2013 so it needed to be refreshed anyway. It even had the old style connector so they needed to buy the new connector and hack that into the wiring harness because the new HPFPs only come with the new connector port.

After the fix I kept using the car for 2 days straight, I drove it for whatever reason just to test it and I noticed that the more I drive it the more it stablizes its fuel trims as close to zero as possible.

I will update my threads when I come back from work and after further testing just to make sure that this time it is 100% fixed.

[Hoa]

Originally Posted by Anwar1995

Hey,

I am not sure if you got your issue sorted but I thought I might give you an update on my issue.

Short answer I think I got the issue fixed and it was the HPFP

That is what I have been telling you in the thread you created about your car's issue.

If a shop uses a scanner, they don't have the proper tool to diagnose your car. ISTA is the best way to diagnose a BMW which you can download for free if you search this forum.

[Anwar1995]

Originally Posted by Hoa

That is what I have been telling you in the thread you created about your car's issue.

If a shop uses a scanner, they don't have the proper tool to diagnose your car. ISTA is the best way to diagnose a BMW which you can download for free if you search this forum.

I saw your post but in my defense I have checked the pressures of my HPFP and it was all within spec range. I still should have listened to your advice and start investigating more on the HPFP but pressures were basicly saying to me that its all good there thats why I did not reply to you there.

The shop that I went to had ISTA which they also used on my car for diagnosis but they first used a generic scanner which seemed to be good enough for them to give a proper diagnosis that eventually solved my problem (or I hope so).

Again Thanks Hoa for your input on my thread and I apologise that I didn't take it as I should.

[AlpineweissF10]

Originally Posted by Anwar1995

Hey,

I am not sure if you got your issue sorted but I thought I might give you an update on my issue.

Short answer I think I got the issue fixed and it was the HPFP.

Long answer:

I took the car to a shop specialized in BMWs and MINIs and they diagnosed the car. They told me that there is control valve on the HPFP that seems to be not working properly. Its called "Quantity control valve". Basically from my understanding it regulates the fuel flow going to the HPFP and when it fails the fuel flow is not being controlled proparly thus the rich condition and the misfires.

What they showed me exactly is that you can read how much percentage wise the valve is operating at using a scanner and in my case it was always at 0%. one would think that this would throw a code but it didn't for some reason. Anyhow when they pulled my HPFP it was the orginal one that came with the car with the manufacturing date of 2013 so it needed to be refreshed anyway. It even had the old style connector so they needed to buy the new connector and hack that into the wiring harness because the new HPFPs only come with the new connector port.

After the fix I kept using the car for 2 days straight, I drove it for whatever reason just to test it and I noticed that the more I drive it the more it stablizes its fuel trims as close to zero as possible.

I will update my threads when I come back from work and after further testing just to make sure that this time it is 100% fixed.

Thanks for the heads-up. Did the issue ever come back? I had given up and taken the car into a euro mechanic near me and they still couldn't figure it out. I ended getting the car back and just parked it in the garage.

I tried to check in ISTA but I can't find where to measure the quantity control valve. Do you know which menu option they used?

[Anwar1995]

Hey,

I got back from work and have been driving the vehicle daily and so far no codes and no drivetrain malfunction messages. It seems like it was actually the HPFP.

They showed me the value of the quantity control valve via a normal scanner in live data, which menu exactly? I cant recall either engine or fuel pressure menus. but it was always reading 0%.

If you have the original HPFP I recommend that you give it a shot.

Good luck and hopefully you figure it out. If you need any more info don't hesitate to send me or reply to this.