Extremely High Idle when clutch is pushed???
 

Hello All

On my 1981 911 SC Targa at start up it idles extremly high (3,000 - 4,500 rpm)when I press in the clutch and give it a little gas. Does anyone have an idea of where to start in solving this issue.

I have played wall flower for years looking at this site and waiting for the day I can participate and write about a car of my own. Now I am here and can share the highs and lows of owning this great machine!

A possibility is that the Bowden cable for the clutch is somehow touching the bellcrank assembly for the TB on the transmission housing.

Clutch cable and accelerator mechanism is close together there.

Welcome to THE Forum SmileWavy
You will find a lot of help here.

A common place for the clutch to interact with the accelerator is a mis-placed clutch cable Bowden tube at the accelerator linkage bell-crank at the transmission. Check to see if the Bowden tube is contacting the shaft of the bell-crank. This is at the rear of the transmission mount on the driver’s side.

It is also possible for the clutch cable to be on the wrong side of the accelerator rod at the front of the tunnel. If this were the case, it wouldn’t be a subtle interaction at all. This is usually undrivable.

Best,
Grady

You say this just happens @ startup? After driving a while will it idle @ normal speed w/ the clutch in?

If so, I would also check the AAR, which keeps revs up during cold warmups, as well as the decel valve, and the sensor plate and its setting.

Thank you very much Gunter & Grady! I will look at that and let you know how it worked out. It is starting to get warm (Spring is on the way) and I am so ready to start driving it more. I see you guys have been on the forum for a while. Trust me... this is the first of many questions from me.

Regards,

Madera

I have only had the car for a month and I have not driven it much. About 4 times. What do you mean when you say a while?

Paul,

I read the thread on the Decel Valve and I don't that is the problem. I get a normal idle at start up. It is when I press the clutch in and then give it gas and let off the gas... it does not go down, but continues to idle high.

binding plastic bushings at the front throttle bell crank as well as the rear one on the trans can also do it. check the cruise cable at the engine throttle. the black plastic end can pop out of it's holder and hang up. a couple of zip ties takes care of that.

Wow! I am impressed with all the feedback that I am getting! I will check it out. I ordered my 101 projects book this week.

Where can I get the most comprehensive diagram of the engine and its components? What book, website, etc.???

Just out of curiosity, After you push the clutch & give it some gas, if it is idiling high, reach down and pull the gas pedel up & see if it drops to a normal idle. (See if the pedel is partially sticking...)

Oh, and for any further direction, were gonna need to see some pics... :D

Madera 911,

What I meant was this: does this symptom occur just @ startup, or does it continue to happen once the engine is warmed up? Say you've been driving a half hour and then pull up to a stoplight? You only mentioned "at startup".

Porsche website has parts diagram available in PDF form:

http://www.porsche.com/usa/accessoriesandservices/classic/genuineparts/originalpartscatalogue/originalpartspdfcatalogue/

MindtrapX

Yes! When I reach down and pull up the accelerator it idles back down.

Pics coming soon!!!

I was curious because my car had the same problem last night. Hopefully this helps in identifing the problem. I'm not sure what causes it to stick, but I'm sure someone here will have a solution. :) Like you, I have only had my car for a few months and just got some shifting issues fixed this week.

Funny, I think I fixed mine today. It would stick @ 2100 rpm. Would correct when I pulled peddle up. Took off the bushings on transmission, cleaned, WD 40 and reassembled. Think the swepco dripped on it during last trany change, making it stick. Seems ok now, need a few days to be sure.

Thanks,

That makes complete sense to me. I will do that and see what happens.