[anthonyscarisbroken]

My n20 has been running rich for a while now and i cannot figure out why. This might be a lot and messy so bare with me. It started stalling on me and the check engine light was blinking. My first thought was vacuum leak but after checking 4 times i moved on. I changed spark plugs (didnt notice any gas or abnormal corrosion), swapped coils, changed the fuel pump (which now it idles a lot better) but im still having loss of power/acceleration. Ive noticed on bimmerlink the O2 sensors are reading fine BEFORE the car warms up. Also the LTFT and STFT are relatively normal on cold start. Aftering letting her run both values were at -30% (O2 is .7 on BL) Im considering just getting a new maf and O2 sensor but other than that idk. I figured if the injector were leaking it wouldnt be running as well on idle but idk im completely lost here. If any of you guys decide to help me id be grateful and give you any more information. This thing is practically my child and i would love to see it back in action. Thank u

[LA1Z24]

Using a scanner, graph the FUEL RAIL PRESSURE with the engine running and hot. Shut the engine off, but key on quickly so you don't lose data communications. After shut down, the FUEL RAIL PRESSURE should RISE and continue to rise as much as 1000PSI! If the FUEL RAIL PRESSURE drops, then the injectors are leaking and should all be changed as a set

[anthonyscarisbroken]

Fuel pressure seems to increase slowly after shutdown so ig thats good right? The only thing i noticed was on idle was the pressure was around 1700 psi. One of the hardest things I’ve realized when looking at values is i have no idea whats normal and what should concern me.

[thejeremyman9]

Good advice above. If your fuel trims are both at -30% either you have a fuel over supply issue (such as injector), or the sensor values are wrong. It sounds like the first one where the car is actually running rich based on observation and the trims are trying to pull fuel to correct that.

[thejeremyman9]

Originally Posted by anthonyscarisbroken

Fuel pressure seems to increase slowly after shutdown so ig thats good right? The only thing i noticed was on idle was the pressure was around 1700 psi. One of the hardest things I’ve realized when looking at values is i have no idea whats normal and what should concern me.

Take a look at datalogs for N20 in the N20 tech forums to get an idea of what is normal range for different parameters

[ProjectRandomCO]

Any update on this? I have been fighting this issue since I rebuilt my car. Cold start and initial drive are perfect but after the car warms up to around 165+ something switches and AFR goes full rich, .70 STFT and the car stumbles and runs like crap. AFRs sometime sit at 10.29 and sometimes at .70 they are on target or close.

If I restart the car while warm the problem persists, as soon as it cools back down it's back to normal.

I have a new battery on the way since mine was pretty weak and won't hold a charge long.
I've checked just about everything, logs from when the car is rich are identical to when it's running normal, only difference is coolant temps and the Lambda controller output is at .70 and the lambda control factor bank 1 is at 10.29. Both upstream and downstream O2 sensors have been replaced, issue is exactly the same.
Car is speed density so no MAF sensor, coolant temps seem normal so I don't think it's the sensor, I cleaned the injectors in an ultrasonic but they could be bad.