Hi all,
This is my other issue with my car that I've been trying to troubleshoot for more than a year
The issue: car initially runs perfect. after staying in heavy traffic for more than 20-30 mins the rpms starts to fluctuate and AFRs go up and down, being correlated by STFTs going to -34% on both banks until the rpm goes back up. So for some reason it tends to go very rich which drowns the engine. If I let it sit like that it starts stuttering so bad that it can even stall. If it stalls sometimes it has a very long crank afterwards followed by a huge black cloud of smoke on startup. If I start driving it hard for a while, when I stop and let it sit at idle it runs great and again after 10-15-20mins it begins the fiasco again. Also, when the rough idle starts happening, if I leave from a standstill very slowly and take off the gas the engine will sometimes stall or nearly stall.
In WOT everything goes well except for a misfire on #5 on very high rpms and only on highboost maps but that issue I am fairly certain is totally unrelated.
I tried changing a lot of parts:
new o2 sensors
all injectors idx12
new hpfp from bmw
new lpfp
new ekp
new crankshaft pos sensor
new coils plugs
new silicone vacuum lines
new fuel tank recirculation valve (or whatever it's called, the valve that connects from the tank to the intake manifold to burn off excess gas vapours)
NO error codes. When idling or driving slowly so that the issue arises, the car always sits in Fuel Mode 2 (normal), very rarely it goes to fuel mode 20 for a split second.
My initial thought was "ah simple, injector leaking", but I tested all of them by connecting them backwards and cranking the engine to see if they leak and none of them do. Secondly, if there was an injector fault, I should see weird AFRs on one bank, not both and in an identical manner in each. The AFRs and STFTs also mirror each other almost perfectly.
My second guess was the hpfp. But sadly getting a new one directly from BMW had no impact. Also, when the engine stalls and it struggles to crank back up the HPFP reading is 6-700psi so it is not a fuelling issue that prevents it from starting.
What could cause so much fuel (or so little air) at idle if everything fuel related is good and I have no vacuum leaks? Also, why on earth does it happen only after the car sits at idle for a long time, and is not more consistent?
Thank you for your time reading this and I hope you have some ideas to help me.
This is my other issue with my car that I've been trying to troubleshoot for more than a year
The issue: car initially runs perfect. after staying in heavy traffic for more than 20-30 mins the rpms starts to fluctuate and AFRs go up and down, being correlated by STFTs going to -34% on both banks until the rpm goes back up. So for some reason it tends to go very rich which drowns the engine. If I let it sit like that it starts stuttering so bad that it can even stall. If it stalls sometimes it has a very long crank afterwards followed by a huge black cloud of smoke on startup. If I start driving it hard for a while, when I stop and let it sit at idle it runs great and again after 10-15-20mins it begins the fiasco again. Also, when the rough idle starts happening, if I leave from a standstill very slowly and take off the gas the engine will sometimes stall or nearly stall.
In WOT everything goes well except for a misfire on #5 on very high rpms and only on highboost maps but that issue I am fairly certain is totally unrelated.
I tried changing a lot of parts:
new o2 sensors
all injectors idx12
new hpfp from bmw
new lpfp
new ekp
new crankshaft pos sensor
new coils plugs
new silicone vacuum lines
new fuel tank recirculation valve (or whatever it's called, the valve that connects from the tank to the intake manifold to burn off excess gas vapours)
NO error codes. When idling or driving slowly so that the issue arises, the car always sits in Fuel Mode 2 (normal), very rarely it goes to fuel mode 20 for a split second.
My initial thought was "ah simple, injector leaking", but I tested all of them by connecting them backwards and cranking the engine to see if they leak and none of them do. Secondly, if there was an injector fault, I should see weird AFRs on one bank, not both and in an identical manner in each. The AFRs and STFTs also mirror each other almost perfectly.
My second guess was the hpfp. But sadly getting a new one directly from BMW had no impact. Also, when the engine stalls and it struggles to crank back up the HPFP reading is 6-700psi so it is not a fuelling issue that prevents it from starting.
What could cause so much fuel (or so little air) at idle if everything fuel related is good and I have no vacuum leaks? Also, why on earth does it happen only after the car sits at idle for a long time, and is not more consistent?
Thank you for your time reading this and I hope you have some ideas to help me.
