Idle drops when clutch disengaged

[NickD]

I apologize if this was covered somewhere, but I couldn't find it. I'm having some idle issues, nothing that keeps the car from getting around, but I just had a simple question. The car can be sitting still and idling fine in neutral with the clutch engaged (foot off the pedal). When I push in the clutch the idle will drop and it will run a bit rougher. This just seems backwards to me as I'm removing the engine's load by pushing in the clutch pedal.

What gives? Is something assisting the clutch that pulls down the idle? I've worked with very few manual cars over the years, and even less foreign cars so I'm a little out of place.

Thanks for any help!

[Ryan]

Sounds backwards to me too. I'll chuck a random and invented theory at you just for fun.

The ECM compensates against load at idle. If you turn enough shyte on, the load is enough to decrease the idle below an acceptable threshold. The engine bumps it up a notch to get you back into a good range. (turn everything off, then hit A/C, full fan, pull on lights to engage dims and brights at once, hit the brakes, and press defog, and turn on the stereo, pull down both windows, move the sunroof, turn on seat heaters, crank the dimmer, hit the domelight, pop the hatch for the little bulb back there, crank the wheel, and get a friend to help. ha.)

Your current conditions leave the car right at the lower limit of one of these step-ups, so when you take off the load, the engine switches down to the lower extreme of the next threshold down.

Or you've got a vaccuum/idle control/air sensing issue.

I'm going to bed.

[NickD]

Sounds backwards to me too. I'll chuck a random and invented theory at you just for fun.

The ECM compensates against load at idle. If you turn enough shyte on, the load is enough to decrease the idle below an acceptable threshold. The engine bumps it up a notch to get you back into a good range. (turn everything off, then hit A/C, full fan, pull on lights to engage dims and brights at once, hit the brakes, and press defog, and turn on the stereo, pull down both windows, move the sunroof, turn on seat heaters, crank the dimmer, hit the domelight, pop the hatch for the little bulb back there, crank the wheel, and get a friend to help. ha.)

Your current conditions leave the car right at the lower limit of one of these step-ups, so when you take off the load, the engine switches down to the lower extreme of the next threshold down.

Or you've got a vaccuum/idle control/air sensing issue.

I'm going to bed.

That's a heck of a scenario! Especially sitting at a stoplight . I've noticed this with at most the rear defog on (but I don't think it was), the a/c on low, and the radio on. At least it was just a running car with everything shut off (tried it in the garage one day). Made no difference.

I had wondered about a vac leak but didn't know if it was tied into the clutch system at all. Same with IAC.

Currently I'm trying to set up to install a ground loop and see if it helps other issues (just stumbled onto that mx3-fix last night). I'm just wondering if this is something completely unrelated.

[4gotn]

ive the same issue after ive Ben driving a while but it really doesn't affect my car too much being i has the idle at 1500 which is almost perfect for the b6
when it tried to die it just drops to about 750
try upping the idle...would help temporarily

[pauleatstoomuch]

Bump.

I have this same problem, and am trying to find a fix.