fbgh2o

My 86 951 seems to idle a little low, but only sometimes. Specifically on arriving at a stop light, about 50% of the time it will drop to about 500 rpm, idle a little lumpily for 10 to 15 seconds (gradually working its way up to 750 to 800 rpm) and eventually settle at around 800 rpm. Once and a while after stabilizing it will go lumpy for a shortly while, but generally prolonged idle is pretty steady.

In the last few months I have replaced all of the vacuum lines (all tied off with zip ties), done a venturi delete, cleaned the ISV and replaced the mounts and replaced the cycling valve. I have tested for vacuum leaks (with carb cleaner at the junction points) and do net seem to have any leaks. What else should I be looking for?

Many thanks.

fbgh2o

Bump

jerome951

Check Clark's Garage procedure for setting the idle speed. It gives a procedure for electrically disabling the ISV. Do that to see if your idle continues to fluctuate. If it still does, it sounds like a vacuum leak.