07 335i single turbo installed now crazy misfires. (info inside)

MilesG

New Member
Oct 20, 2022
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I have a 07 335i with a speedtech single turbo kit that I just installed. It’s running jb4 with custom MHD bef. The car ran fine before the swap but now I’m chasing a big issue. I’m getting constant misfires on all of bank 2 cyl 4, 5, 6. It is very present at idle but here’s the weird part! If I clear the fuel adapts it will run absolutely perfect… for about 5 mins then it will slowly start to go back to running like ass. I’m running the o2 sensors in the downpipes not the manifold where they get way overheated. I have seen people do this before so I decided to give it a shot. I really cannot see how this could cause an issue Seeing how all the other turbo cars we build (not bmw) run this way. I have replaced plugs, coils, vanos, mosfetts. It’s not an actual misfire because resetting the adaptive wouldn’t fix that. Any ideas ?
 
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Torgus

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Nov 6, 2016
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Boston
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I have a 07 335i with a speedtech single turbo kit that I just installed. It’s running jb4 with custom MHD bef. The car ran fine before the swap but now I’m chasing a big issue. I’m getting constant misfires on all of bank 2 cyl 4, 5, 6. It is very present at idle but here’s the weird part! If I clear the fuel adapts it will run absolutely perfect… for about 5 mins then it will slowly start to go back to running like ass. I’m running the o2 sensors in the downpipes not the manifold where they get way overheated. I have seen people do this before so I decided to give it a shot. I really cannot see how this could cause an issue Seeing how all the other turbo cars we build (not bmw) run this way. I have replaced plugs, coils, vanos, mosfetts. It’s not an actual misfire because resetting the adaptive wouldn’t fix that. Any ideas ?

Nope!
 
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