Help for idle
 

My '77 911s just started with a new mystery. At idle ( 1100-1200) it was fine until I drove for a while. Then when ever I stopped the idle would slowly climb up to 22-2300. Stopped at a local P-car wrench and showed him the problem. He said something about there being a leak into the air box or something. Nursed it home and all of a sudden the problem went away and stayed away for the rest of the day on trial runs. HELP with any ideas:rolleyes:

Likely an air leak. Take a can of carb cleaner with the red straw to focus the spray. Start spraying small amounts around the intake next to where they bold to the engine, then the various vacuum hoses. If the idle increases a little, that is your culprit. Carefull when spraying around the air intake, it will suck into engine and increase the idle, making you think that is where your problem is.

That is the first and cheapest place to start, if that doesn't work, you are into chasing an intermittent bad part.

Try checking the common areas for leaks, like the rubber intake runners from the airbox, the fit of your popoff valve, the vacuum lines throughout, and especially the decel valve. Try plugging the top line to the decel valve. Also, be sure your mixture is set correctly-not too lean.

If you search you will find further info.

idle problem
 

Thank you guys for the suggestions.Still it doesn't make sense because the whole problem went away. Could dirt in the air intake cause it? Today the car ran fine and did not do it at all.

I've heard this from several 911 CIS owners over the years, and it is almost always the way you describe it-intermittent, but usually coming to a stop after a long high speed run in hot weather conditions. See if it comes back in a few days.

idle problem
 

Thanks PaulP. A little more detail--- I drove the car from an elevation of aprox. 5,000 ft down to 800 feet when it showed up. Temp was 60-65. On the return trip was when it diappeared. Total round trip was aprox. 65 miles. Does that help in any way to come up with the trouble?-----Bob:confused:

I think so. Your WUR for a 77 may not have a chamber that allows for enrichment @ higher altitudes so your CO may be set richer to get it to run right where you usually drive, so it would be wrong @ lower alts.

Alternatively, you might have a faulty or incorrectly set WUR or an air leak in this system.

If you try

http://forums.pelicanparts.com/uploads3/WUR981085747240.gif

you will find some info on the types of WURs out there.