Idle goes up to 2000 when at light?
 

Any one know why this is happening. When I stop at light the idle goes up to about 2000 rpms and then stays there. IF I let out the clutch and don't touch the gas I can bring it back down to a thousand rpms where I want it. So what is wrong? Almost like something is sticking!

I'd guess the throttle cable is getting hung up spomewhere. Trace it all the way back and tie up whatever is in the way. You don't want to end up like this post
http://forums.pelicanparts.com/porsche-911-technical-forum/152045-ouch-runaway-throttle-please-read.html

John

depends, what car do you have?

on early 911's , with MFI , it can happen
i have it on my '73 S, intermittendly

if i put my right foot on the brake, and slightly release the clutch while in gear, my RPM's drop to 800 and they stay down till the next light...

doesn't always do the high idle.. depends, athmosferic conditions maybe.. not sure

Car is a 1978sc with no cruise control.

John is right. Your clutch cable it wrapped around or rubbing on your throttle cable. It's just enough to give your car some gas. It is usally happening in the center tunnel near the pedals.
To make sure have the car out of gear and pump the clutch pedal a few time to see if it continues to do it. Hope that helps

Actually when I let the clutch in and out I leave it in gear and that strain on engine is what brings the rpms back down to 1000 rpms where I have my idle set. Then it stay at the right setting untill I drive too next light and the same thing happens. When I start the car the idle is right where it is supposed to be, only after I drive and let it rev up it stays high. Also if I'm at a light and the idle is right and I blip the throttle or push down on gas pedddle it will stay elevated. Any hellp here?

I was having the same problem after I replaced the O2 sensor. I did the clutch trick which seemed to work sometimes. Finally, I just turned down the idle thinking that revving the engine a little would be easier (and less embarrassing) than sitting at a light at 2k. When I did that, it seemed that it was no longer a problem and I don't even need to feather the gas to keep it from stalling. Maybe this will work for you.

Good luck.

My 83SC does this intermittantly when it gets hot. I think it's sticky mechanical advance parts in the distributor. When I put the clutch in, the RPM's drop to 2000-2200 and hang there unless I let out on the clutch a little. If I don't let the clutch out far enough for the RPM's to drop around 1200, they slowly rise again. I plan on pulling my distibutor for a good cleaning soon.

try disconnecting the "deceleration valve" hose.. plug the hose afterwards.

I have rebuilt and liberally greased my distributor and disconnected the decel valve after having the same issues on my SC. The problem still happens once in a blue moon, but nowhere near as frequent as it did before those two fixes. Try those along with the throttle cable trick. That's next on my list.

Cheers,

Brad
'83 SC Coupe

Just like too thank all of you. I will try all your recommendments.

O.K.. I also have this problem with my 79SC. It only happens after the engine is warmed up and the weather is warmer. I tried the "disconnect and plug the deceleration valve hose". It worked to keep the idle down but before the engine fully warms up the idle will drop to the point where the car will almost stall then bounce back to normal 950 rpm (sometimes it does stall). I've used the "clutch method" and even turned on the air conditioner (seems the parasitic drag of the compressor is just enough to keep the idle down). If I disconnect the decel valve should I bump up the idle speed to keep the car from stalling when cold? I don't think its the clutch cable interference thing. Any suggestions? Thanks in advance.

Funny I have exactly the same thing on my 1978 sc, it's not that frequent but seems to be worse after I haven't driven for a while.

Gerko.