I have a 1994 540i automatic. It runs perfectly at idle and under normal acceleration but if I put the accelerator down all the way the revs start jumping between around 3,000 and 3,500 cycling about twice per second and the jerking is quite violent. It does not seem to matter if the engine has been running for some time or only just warmed up. Mechanic thought it might be the flow sensor on the air intake and replaced it but this made no difference.
Any ideas?
Is it able to exceed 3,500 rpm? IS this the only band of speeds that it bucks?
Current fleet:
1999 BMW e36 M3
1999 BMW e36 328is with rotary valve engine head
1999 Oldsmobile Eighty Eight
1990 Jeep Comanche Eliminator
1962 Austin Healey Sprite
If I don't plant the foot yes, revs will go right up to redline. In normal driving it is fine. It is only when I try to accelerate maximally that the bucking occurs and even then not everytime.
Are there any CELs on the dash? If so, it may be helpful to pull them. So far it sounds like coils to me
primum non nocere
This one has me pretty stumped. I have not experienced such a thing in any vehicle.
It sounds like some weird fuel issue to me. Is there a possibility that your fuel filter is clogged or you fuel pump is dieing?
Current fleet:
1999 BMW e36 M3
1999 BMW e36 328is with rotary valve engine head
1999 Oldsmobile Eighty Eight
1990 Jeep Comanche Eliminator
1962 Austin Healey Sprite
No CELs on the dashboard :-(
This is a tough one and certainly has stumped my usual mechanic.
MAF, plugs, coils would be the first things I look at
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Thanks. Good suggestions. Can I ask what MAF is?
MAF is Mass Air Flow sensor. Every fuel injected car has it and it is located in the intake piping prior to throttle body. It basically calculates amount of air flying by and communicates this information to the ECU.
primum non nocere
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