3.2 high idle
 

Greetings all, I just purchased my first porsche. It's an 85 911 Carerra. White gold, matching wheels, whale tail, tan interior. 99.5 k miles. The car starts and runs great, but the idle will stay high ( 1800 rpms) sometimes. I cleaned the idle control valve, and am running some Techron through the system. It starts from cold well, and pulls strong with no surges, but it seems that after the car is warmed up, when I come to a stop, the idle will go to 1800 rpm or so. If I give the gas a quick jab, it usually will then drop to 800 rpm, and be a smooth idle. I have not had the chance to clean anything else yet, ( air flow meter ). Any guess on what it is. Is something gummed up in the throttle control. Can I spray any intake cleaner into the system if I take the air cleaner off. Please advise.... I have only had the car since Saturday, adn love it so far, other than the goofy idle. I have been prowling this bbs for a while now, and have learned the little I know about Porsches from here. Thank.http://forums.pelicanparts.com/uploads6/11130432559.jpg

I'm guess your linkage may be binding up and keeping the engine from returning to the idle position. There is a switch on the engine which lets it know that the linkage is at idle. You should be able to check with an assistant if the throttle linkage is returning to the idle position.

Doug

Doug,
Thank for the reply. I will check it out. However, I can make it go to high idle from the engine compartment by giving it a little gas by hand ( from the throttle linkage), and it will stay at the high idle, even though the linkage is in the idle position? Is there anything internal that I can't see that could be sticking or binding. Also, what service manuals do you suggest. I am a fair mechanic, and plan on doing as much myself as I can ( nearest Porsche dealer or repair is 200 miles away). Thanks again.

Check your Idle Position Switch. There should be continuity with the throttle closed and in all other positions except aprox. 1mm open. This is checked with the engine off.

Nice car and welcome to the board.

Thanks Jeff,

I have no manuals yet. Where is the Idle position switch located. I am a Radiology service engineer, so I know my way around electronics. I can test the switch, just need to know where it is... thanks again....

Very nice car. Welcome to the board.

Two microswitches - left hand side of the throttle body opposite the air cleaner.

The top one is the Wide Open Throttle switch, make sure at full throttle it is engaged.

Bottom is the idle control microswitch. If it is not properly triggered it can make the idle fast.

Hopefully you can see on the left side of this picture...
http://forums.pelicanparts.com/uploa...1130438797.jpg

Good photo above. On the right side of the throttle body, just below the elbow shaped rubber tube there are two plugs. to test the idle position switch unplug the top plug and check for continuity across the two prongs. On the other side of the throttle body more toward the front is the adjustment screw for the switch (straight behind, toward the front of the car, from the spring in the left side of the picture). Basically you are just changing the resting point of the throttle linkage.

Thanks for the information guys. Excellent picture and tech descriptions. I will check it out today.... I love this board..thanks again. by the way, the car must have been sitting and not driven much before I got it, the high idle problem seems to be getting a little better the more I drive it, and it definitely seems mechanical, (not a sensor), since i can make it return to idle every time by jabbing the throttle. I am hoping that it is just an adjustment with the above mentions switch. If not, I will clean the throttle body and check for binding...

Welcome and congrats to what I believe is the best year model 911. Looks brand new !

Where is ND ? New Dehli ? ;)

With the engine running, push throttle lever closed (in engine compartment) with your finger or pull the gas pedal up with your toe. If the idle drops, linkage is too tight, binding, or the carpet is pressing on the gas pedal.

To test the idle switch for activation:
With the engine off, pull throttle lever barely open (in engine compartment) and listen for the faint click of the "off idle" microswitch.

Leave the adjustment screw alone.

-Chris

Thanks Markus, I really like the looks of it too. It seems ( so far) that I got a good car. It lived most of its life in a nice dry desert ( Arizona), so no rust. It still is wearing its original paint, and has the original interior. It has a couple oil drips, but from what I have read, that seems normal. The car will continue its pampered life in my care...http://forums.pelicanparts.com/uploa...1130506615.jpghttp://www.pelicanparts.com/support/smileys/grin.gif

I would really like to see some interior pics if you have them. Especially wheel - dashboard part.

Spooty,

If your distributor advance springs are not pulling the advance weights back to the idle position, you will get a high idle. It could be that the weights just need cleaning to move freely.

Rex

Thanks for the reply Rex. I'll check that as well. Markus, here you go....

http://forums.pelicanparts.com/uploa...1130512190.jpg

a couple more....
http://forums.pelicanparts.com/uploa...1130512340.jpg

Wow, its in fabulous condition. Great color combo !

Do you have heated seats ? If so, where is the control nob for that ? The Bentley manual seems to suggest they are next to the electric seat controls on side of seat. But mine are on center console next to A/C control. Strange.

Guys, you are my heroes!! I went out to the car, and measured the idle position switch. I could hear it as well, and it was on the hairy edge of making/breaking. I adjusted the screw(with lockdown nut) to allow the linkage to "make" the switch more solid ( but not too much) and the car runs like a dream. No more high idle!! You guys made my day. Hopefully I will be able to return the favor someday. By the way, Chris, why do you say to leave the adjustment screw alone? I can see no other way of adjusting that switch other than with that screw. Please advise...