2008 E90 with 2.0 N43, VIN : A412008, Mileage: approx. 100000 miles
First looked it at about 10 days ago, customer had already changed low pressure sensor due to fault code but now found fault code for misfire cylinder 1, so customer changed coil but still no difference. Also had fault code for air mass meter and NOx/Cat convertor oxidised.
I performed ISTA guided misfire test which suggested to change all injectors. (makes a change from suggesting changing all plugs/coils/injectors![bigsmile2]( "bigsmile2")
).
As customer had spare brand new injector I advised to fit this to cyl 1, and swap MAF from another car as test.
Went back end of last week, misfire fault code gone, but MAF fault code still randomly coming back (cat fault always present). Can feel random misses at idle, smooth running numbers show no particular cylinder to blame.
However now on medium to heavy throttle, car stumbles, sometimes rpm slowly bounces around 1500-2000ish, sometimes it will gradually climb, but on gentle throttle, it runs nice and will happily and quickly rev to redline.
I noticed when car was good, fuel rail pressure was approx. 150000mbar, but when car misbehaved, fuel pressure would drop as low as 8000mbar.
(LPFP in tank makes approx 5000mbar itself).
So my next recommendation was to change HPFP.
Went back today and car behaving exactly the same, but the only difference is now fuel rail pressure normally around 150000mbar, but full throttle would increase rail pressure to approx. 200000mbar.
However car still behaved exactly the same so I thought to inspect throttle body which was clean, but I noticed with gentle throttle input, I could feel suction increasing all the way to redline.
With medium to full throttle I could feel air pumping OUT of the throttle in time with engine RPM.
Reconnected it and noticed if I removed the cover for MAF, I could feel heavy air pulses coming out here as well.
If I removed oil cap, could feel moderate air pressure coming out, and engine RPM would slightly drop and become more rough.
I have to admit electrics is more my specialty and I don't think this is electrical at all so would be very grateful for any input from anyone who has any idea.
I thought today maybe problem with DISA (maybe one stage partially blocked, or not correctly switching), but I could not find any DISA valve or motor, and I could not find any live data or actuation's, and no mention of DISA when looking up manual to remove/install manifold in ISTA and TIS.
The only remaining crazy theories I can come up with:
Exhaust/Cat blocked. But I can hear Metallic rattling from exhaust occasionally, just like damaged cat which matches with fault code for cat. Also if exhaust blocked, I doubt engine would happily spin up to red line with gentle throttle.
Inlet valves sticking. Maybe because of direct injection, inlet valves covered in rubbish, so sometimes struggling to close. But then valve should be smashed to bits by the pistons from sticking open, and compression test would show nothing as problem is only with medium to heavy throttle.
First looked it at about 10 days ago, customer had already changed low pressure sensor due to fault code but now found fault code for misfire cylinder 1, so customer changed coil but still no difference. Also had fault code for air mass meter and NOx/Cat convertor oxidised.
I performed ISTA guided misfire test which suggested to change all injectors. (makes a change from suggesting changing all plugs/coils/injectors
).As customer had spare brand new injector I advised to fit this to cyl 1, and swap MAF from another car as test.
Went back end of last week, misfire fault code gone, but MAF fault code still randomly coming back (cat fault always present). Can feel random misses at idle, smooth running numbers show no particular cylinder to blame.
However now on medium to heavy throttle, car stumbles, sometimes rpm slowly bounces around 1500-2000ish, sometimes it will gradually climb, but on gentle throttle, it runs nice and will happily and quickly rev to redline.
I noticed when car was good, fuel rail pressure was approx. 150000mbar, but when car misbehaved, fuel pressure would drop as low as 8000mbar.
(LPFP in tank makes approx 5000mbar itself).
So my next recommendation was to change HPFP.
Went back today and car behaving exactly the same, but the only difference is now fuel rail pressure normally around 150000mbar, but full throttle would increase rail pressure to approx. 200000mbar.
However car still behaved exactly the same so I thought to inspect throttle body which was clean, but I noticed with gentle throttle input, I could feel suction increasing all the way to redline.
With medium to full throttle I could feel air pumping OUT of the throttle in time with engine RPM.
Reconnected it and noticed if I removed the cover for MAF, I could feel heavy air pulses coming out here as well.
If I removed oil cap, could feel moderate air pressure coming out, and engine RPM would slightly drop and become more rough.
I have to admit electrics is more my specialty and I don't think this is electrical at all so would be very grateful for any input from anyone who has any idea.
I thought today maybe problem with DISA (maybe one stage partially blocked, or not correctly switching), but I could not find any DISA valve or motor, and I could not find any live data or actuation's, and no mention of DISA when looking up manual to remove/install manifold in ISTA and TIS.
The only remaining crazy theories I can come up with:
Exhaust/Cat blocked. But I can hear Metallic rattling from exhaust occasionally, just like damaged cat which matches with fault code for cat. Also if exhaust blocked, I doubt engine would happily spin up to red line with gentle throttle.
Inlet valves sticking. Maybe because of direct injection, inlet valves covered in rubbish, so sometimes struggling to close. But then valve should be smashed to bits by the pistons from sticking open, and compression test would show nothing as problem is only with medium to heavy throttle.