A blown head gasket will distort the idle in that it will cause a missfire as water or oil gets on the plug and fouls it out. An air leak of somesort is what will cause the higher idle speed. If you have an air leak in the tube anywhere before the butterfly valve then the idle will be lower because of not allowing the airflow meter vane to open like it should. Anywhere on or after the butterfly valve will cause the higher idle. I could be the cable that is not allowing the throttle to close all the way, or a gasket blown out somewhere along the intake.
It could even be your distributor. It may have come loose and is advanced too far. There are enough vacuum hoses to cause the higher idle and like the girl said, spray WD 40 around the intake and hoses, lightly, and see if the idle changes any. You could also get a stethescope and listen carefully and see if you can hear a place where air might be getting in unwanted. If you find a BHG, then never mind, as that has to be fixed first.
Even the idle speed control valve could go bad.
Russ
|