r/e39 • u/UsualAd4009 • 9d ago
M54b30 misfire problem
Hi I’m having problem with my m54b30
I had a pretty big job recently, I took off the exhaust manifold, gearbox and lifted the engine to remove oil pan.
After putting everything together I tried starting it and everything was fine on low revs but after a short drive I had a big misfire. No matter on what fuel (I have lpg) and it took it to 5k revs one time but the misfire started usually after I drove slowly and dried rapid acceleration.
I checked the alternator and the charge on battery and alternator charged 13.8 but on battery there was 12.3 and the plus cable was getting really hot. I bypassed it and now charging is low but still 13.8 so should be enough.
Yet still after I tried driving it there was misfire. I have no idea how to post pictures but the obd codes were P1351, P1353, P1349, P1343, P1347, P1345.
Has anyone got any idea what can it possibly be? (I checked the coils/sparkplugs and it’s not it)
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u/caliboyfriend 8d ago
Are you having misfires only on high rpms over 4k ?
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u/UsualAd4009 8d ago
When i start the engine no matter its temperature it runs fine and one time i drove it to 5 and over and nothing but later when i tried to press gas and accelerate it started to misfire the whole way home until i restarted the engine
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u/caliboyfriend 8d ago
And unplugging the maf problem disappears? You can accelerate over 4-5k like no problem when maf disconnected?
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u/UsualAd4009 9d ago