1997 e36 m3 misfire help

[m3f_Shkreli7]

I recently purchased a 1997 m3 with around 63k miles on the car and it misfires in cylinder 6 and sometimes cylinder 5. When the car is cold it doesn't misfire but when it gets warmed up it starts misfiring. Also when I'm driving the car it doesn't misfire only at idle. I have swapped out the spark plugs, coils, injectors, cleaned the idle control valve, checked for any vac leaks, swapped out the man from a working 97 m3, did a compression test and all cylinders were good. Im wondering if I'm missing anything else before I rip up the engine and check the head.



P.S the car was sitting for around 6 years, the owner said he replaced the fuel pump and filter but maybe he could have made that up. I might check to see if the car is getting enough fuel this weekend. If anyone else has some other ideas that I haven't tried please let me know. I really doubt that its the head because it doesn't show any symptoms but maybe a bent valve? Maybe camshaft position sensor?



Let me know what you guys think, thanks.

[m3f_Nate047]

Did you try cleaning the MAF sensor?

[m3f_Shkreli7]

Yea cleaned it and still same problem. Swapped in another one, it was running great for 10 minutes than the problem came back.

[m3f_Eclipsetrbo420A]

Sure its not a vac leak? sounds very likely. did you do a smoke test?

[m3f_Hasan Shaikh]

I doubt fuel delivery will be the issue at idle. Especially since it runs fine at higher rpms.


However, it can be your active carbon filter. Try cleaning that. Maybe its clogged.

[m3f_Eclipsetrbo420A]

How are your grounds and ignition harness? Heat builds resistance so look there too. Swap 02 sensors


Also can you see your fuel trims adaptations? Have you scanned for any stored codes?

[m3f_LuckyM301]

if it only misses when warm I would check sensors

coolant temp sensor to DME or o2 sensors? your obd2 so I'm surprised you don't get codes but if it's 5 and 6 maybe knock sensor?


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[m3f_Shkreli7]

The only codes I get are the misfire 6, misfire 5 sometimes. And sometime a maf code will pop up or a o2 sensor code but both the o2 sensors and maf have been changed.

[m3f_LuckyM301]

so you haven't had a smoke test yet right? if it's spitting out those codes and you've replaced what you mentioned I would smoke test it or atleast check all hoses by the boot and intake manifold

there are some small hoses underneath the manifold as well


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[m3f_Euro Spec 73]

I recently purchased a 1997 m3 with around 63k miles on the car and it misfires in cylinder 6 and sometimes cylinder 5. When the car is cold it doesn't misfire but when it gets warmed up it starts misfiring. Also when I'm driving the car it doesn't misfire only at idle. I have swapped out the spark plugs, coils, injectors, cleaned the idle control valve, checked for any vac leaks, swapped out the man from a working 97 m3, did a compression test and all cylinders were good. Im wondering if I'm missing anything else before I rip up the engine and check the head.


P.S the car was sitting for around 6 years, the owner said he replaced the fuel pump and filter but maybe he could have made that up. I might check to see if the car is getting enough fuel this weekend. If anyone else has some other ideas that I haven't tried please let me know. I really doubt that its the head because it doesn't show any symptoms but maybe a bent valve? Maybe camshaft position sensor?


Let me know what you guys think, thanks.

If you've done all that work already and tuned it up and replaced All Those sensors you mentioned above I would definitely replace the throttle position sensor TPS sensor that sounds like your main issue right there as far as the idling goes or it could be a bad ECU and mostly if this is a swapped out motor and you didn't swap out the correct ECU to go with it you'll definitely have misfiring issues I would consider getting the right ECU and that should help solve the problem.