weird stumble?

[redhead]

I am having a weird stumble under the following conditions.

- idle up to approx. 2800 rpm
- partial to medium throttle
- more noticeable while accelerating not at a constant rpm
- doesn't seem to be temperature sensitive

It feels like a spark plug is bad but they all check out. It is not your traditional misfire but it almost feels like minor bucking. Tried a different set of wires same thing. Air filter in good shape, tried Lucas fuel system cleaner no difference. Under medium-WOT it is perfectly fine in this rpm range. The car pulls hard otherwise up to redline.

Any ideas what it could be?
Thanks gang,
Eugene

[asubimmer]

fuel filter clogged?

[bmwman91]

This sounds like an intermittent issue I have had with my current M42. It mainly does it on the highway under low-load/part throttle conditions. It rarely does it, and I cannot tell if it is just bumps in the road causing driveline busking with the engine putting out minimal torque or what. It is unnerving to haev the car bucking though. I have noooo idea what it is, and I have done all of the above, and the fuel filter like 4000 miles ago.

[redhead]

If the fuel filter was clogged wouldn't the stumble get worse with a greater load asubimmer?

[Ramblin MAn]

Sounds like my problem but not as severe.

I just bought a used complete intake with everything still attached and the crank and cam sensors thrown in plus a wiring harness with relays included.

I've already replaced the ECU and chipped it just for good measure and replaced the O2 sensor.

I will find the prblem even if I have to go back to the stock manifold.

[asubimmer]

If the fuel filter was clogged wouldn't the stumble get worse with a greater load asubimmer?
actually prob, but its good to do anyway and its cheap :D

[bmwman91]

Sooooo...anyone have any luck figuring out the bucking culprit? The car did it to me again on the highway tonight. I can feel it start...it is a slight bucking. If I keep my foot in exactly the same position when it starts, it gets more and more violent. Finally, if I let off the throttle momentarily, it goes away. The car pulls had up to redline...this only happens under low-load still....usually around 3000RPM with the MPG indicator around 25 (and the MPG gauge is an indicator of load). Grrrr......sooo disconcerting!

[asubimmer]

maybe a crank sensor goin out?