Engine "Flutters" at Low RPMs

[CosmosBlack]

[QUOTE]If I have the engine running with my car stationary in "park" position, I step lightly on the accelerator pedal and hold at anywhere above smooth idling and below about 2000rpm, the engine kinda "flutters" (don't know the exact word to describe it). It's like you can feel very minute misfirings, or as if there is this "bubbling" feel like in the old engines running with the choke lever on. When I step on it more and bring the rpm up past 2000, it runs normal.

Same thing when the car is running in gear and moving from stationary or cruising slow below 2000rpm, except that I don't feel it that much unless I pay close attention to it.

Has anybody experienced this before? Is this normal, I don't think it is.
It might have something to do with the "Service Engine Soon" light that is on now and that I'm trying to figure out what the fault is. DIS showed a vague "fuel mixture too lean or rich" problem. I had just replaced a faulty oil separator and thought that was it, but the light came back on.

Thanks.

By the way, it's a 2000 540iA

Guess what? I was at my mechanic's today and was told that I need a new Throttle body/valve. The symptom/fault has something to do with the engine trying in vain to search for an idling speed at low rpm's, but when it goes faster at higher rpm's it goes out of idling mode and so seems to be fine. (If I understood him correctly!) Anyway, it's an expensive part, gonna cost about $600 and $130 labor to install it. I also have an option to install a Dinan part which I was told will add about 8 to 10 hp to the performance.

Does it make sense at all?
Any feedback or similar experiences?
I will be given several pricing options tomorrow before the parts are ordered.

ExTech! Any Ideas?

[Nikk]

I have the same problem. For me, I find that I've had to start giving the motor a lot more revs to get away cleanly from a standing start. It does seem to be variable though and the dealer could not find anything on the OBD to say that the engine's firing badly. If your solution worked, let me know. Thanks

[CBA]

when your engines at idle it runs in open loop to allow information in and out of certain sensors the diagnosis sounds correct i had to diagnose a caddy like that. when you run the car above a certain rpm it goes into closed loop and runs fine.. if they have an approriate scan tool that shows the engine run diagnostics its very easy to calculate. sounds like the dude saved you some money running diagnosis cause figuring that out with noid lights and a multi meter is a bitch. either way diagnosis is correct.

definetly go dinan