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Random Stuttering?

1K views 5 replies 2 participants last post by  HerbP 
#1 · (Edited)
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#2 ·
Hello everyone,

I have a 2009 650i that just hit 60k miles. For the past 6 weeks or so, the car has been stuttering when driving down the street after a cold start (overnight in garage). I feel it the most when I accelerate to 20mph and then let off the gas pedal. The car stutters/shakes... it is a weird feeling. I had a misfire in cylinder 8, and ended up replacing all 8 spark plugs/coils two days ago to make sure they would all be good, but it did not fix the problem. I don't have any codes... so I'm at a loss. Could it be the fuel pump? Wouldn't I be getting a code from that?
That would act like a bad COP, but they rarely ever fail. I would check your fuel rail pressure at the manifold, & I don't think a fuel pump that is acting up would throw a code? I would try & run some Techron in the fuel tank to see if you possibly have a fuel injector that is acting up. I would also try cleaning the MAF sensor to see if it is causing your fuel/air ratio to be off. Check the air intake pipe that connects the air box to the intake to make sure it has not come loose, or has cracked from age.Last thing would be to check the diagnostics on your O2 sensors, to make sure they are operating properly. This can be done with almost any code reader, or your other tool that you have. Using INPA to measure your cylinder efficiency will help point out a problem cylinder.
 
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