well... I guess the subject sort of describes my problem... when the engine is cold, it runs smoothly... but when I push the clutch down and push it into gear (without letting go of clutch) the rpms rise...then drop.. rise.. tehn drop...rise... then drop... even if I leave the car to warm up to normal operating temperature and come back... it doesn't do it while I'm driving, just while I'm in stopped and in gear. It goes away after about 4-5klm of driving????? any idea's?

 

My friends car had this problem, but it might be something different. My friends spark plugs old and nasty and his car would do this, but it would go away after hard driving, I don't know why it would only do it when in gear though. Replaced your spark plugs lately?

 

I have the same problem intermittently(when my car is running that is) i think its a problem somewhere in the cold start system that is supposed to idle at higer rpms until it warms up

 

EXACTLY! I've noticed that it wants to idle like its warm (around 750rpm).... when I start it from cold once and a while the engine will die off and end up stalling (in neutral)...

 

Have you preformed the TB mod? That will screw up your "choke" and cause your car to idle like that.

 

Mine was doing that when the throttle position sensor was out of whack.

Here's how mine would go:
Start.
1/4 the way to full warm.
Idle smoothly dropped from 23-1800 over a few min.
Idle began dropping and picking up from 18-12-18-1200 etc etc.
Car finish warming up, idle fine 750.

 

The reason i'm pretty sure it has to do with the high idle warmup is because the pace of the revving slowly decreases as the car warms up, until eventually stopping and going to normal idle at around 800. I think it's a weak connection in one of the sensors. The voltage in some circuit gets above the threshold to hold it at high idle, so it tries to drop to low idle but the voltage drops due to the weak connection and general age and crappiness of our electrical systems. when the voltage drops below the threshold it signals the system to go back to high idle which increases the voltage so it thinks it can go back to low idle and around and around we go. this is just a theory though, i've had much bigger problems to deal with so i haven't had time to look into this one.

 

Hmmm..... well there hasn't really been any mods to it...other than the polyurethane engine mounts and the straight pipe. I'm thinking it might be the cold start sensor...

 

my car sometimes does that. Possibly a vacuum leak.