Throttle seems to get stuck..

[yagottaloveit]

Hi all,

lately if I drive my 97 M3 a little harder, or after a little bit of driving the throttle seems to be getting stuck. For instance, anywhere between 2000 and 5000 RPMs as I accelerate, if i suddenly press the clutch all the way in, the revs stay at that level for a few seconds and then very slowly go down. If at that point I go ahead and change to a lower gear, the revs will go down at the right level and everything acts as it should.

A couple more things; I have cleaned the throttle body a few times (this did not do anything for my problem); also it seems that this only happens when I actually drive the car; if I'm parked and rev it up, it comes back down to idle quite quickly!?!

Anybody have any suggestion of what i can do to fix this??

Thx

[Soon2bM3]

It might be calibrated to do that. There are actually a few threads about this floating around the different forums. That's the idle speed electronic dashpot control. It keeps your rpms up so the weight of the car doesn't transfer to the front due to sudden engine braking.

Imagine this....driving WOT in 2nd gear entering a rolling corner, then dropping the throttle as you enter a turn instead of rolling off normally. If immediate engine braking occurred (rpm's not sticking), your vehicle weight would transfer to the front wheels. This would make the car unload the rear, causing snap oversteer (aka...spinout). By keeping the rpm's up after lift-foot, engine braking is delayed....keeping poor drivers on the road a little bit longer.

I thought this was weird when I got my first bmw, especially after driving japanese cars for so long. I'm still getting used to it, but I do like it better than the heavy engine braking that comes will many japanese sports cars.

[yagottaloveit]

I dont think its a calibration issue here; i had this car for about a year now, and just in the past month or so, the RPM started "sticking". When i say that i mean, its at 4K, i depress the clutch fully and the RPMs are still at 4000 and they go down very very slowly, up until, lets say 2500, and after that point the go down at the speed they should. Some have suggested the throttlecable having some wires broken, but this only seems to partially be true in my case; what is weird is that the issue only occurs when i drive the car, if its parked and I rev it up the RPMs come down naturally.

[Soon2bM3]

Interesting. Well, my 328 does the exact same thing...I'm just not sure how the severity of the rpm-hold compares between our cars. I'm pretty sure that mine is just a normal setting. There is the possibility of the throttle sticking on your car. That's something I would definitely check out.

[19Rookie83]

This explains everything! I was just wandering this morning when I got out of my car if there was any upgrade I could do that would make the throttle come back down faster. As it seems to float a little. This is fine for normal driving but when driving spirited it makes it a little rough as you are shifting faster than the RPMs can come back down.
Is there any mod you can do to ditch this system? I am smart enough and skilled enough to know that you DO NOT come off the throttle in a corner. It is like a motorcycle you roll on or your die!

[Trptguy]

Check the plastic air flow boot. This just happened to my car. The air intake hoses and boot were cracked causing some vacuum problems

[bennyfizzle]

Chip It And Get A Lighter Flywheel!!!

[yagottaloveit]

For me this "sticking" is only noticeable when the car is hot. Say for instance, i just drive normally for 5-10 mins for the temp to be up, then a quick red-line through 1-2-3, in 4th at 5000 with the clutch all the way to the ground, i can sit there and look at the damn revs coming down as slow as they possibly can... After this, i pull into the garage, car still running, rev it up and everything is normal, the revs come down as they should. I'm wondering if maybe this doesn't have something to do with my clutch, perhaps, maybe when the pedal is fully depressed (as am I) the clutch still grips a little...

[Soon2bM3]

What makes your description strange is that your engine speed stays at the same level with the go-pedal off and clutch disengaged. If your accelerator cable was sticking, keeping the throttle plate in the last open position, your engine speed would increase once the clutch pedal was pushed to the floor.

As for the clutch....the only reason I could think of, other than some strange malfunction, is that there might be a problem with the hydraulics that causes your clutch to remain slightly engaged even with the pedal on the floor. This, however, would probably be noticeable hot or cold, stationary or moving.

I have two other ideas other than what's been discussed, but I must marinate on them a bit before trying to explain.