Expert: John Kingery - 1/25/2011

Question
I have a 1996 BMW 750il when i give it heavy gas i get a po300 with random misfire on 7-12 po307-po312 if i clear the code and baby my driving habits i will not get the code any ideals of what could be the problem I have changed the plugs and the carbon deposits were the worst i have ever seen i also changed the cap and rotor on that side of the engine the car idles good and runs well if i don't give it heavy gas i hope the additional information helps you help me.

Thank you,

James

Answer
Sounds like you haven't determined if the random misfire is from one cylinder or bounces around the 7-12 bank.

When you changed the plugs, did you do both sides?  If so, was there a difference between them?  Was one cylinder bad, or the whole 7-12 side, or both sides equal?

The next two areas I would check are the coils and the injectors, or possibly the fuel pump, depending on what you know about whether one cylinder or one bank.