I have an ls3 crate motor in my 61 vette and I am starting to have problems with high idle. When I come to a stop at a traffic light sometimes the idle will stay high around 1000 rpm's and other times it will drop down to normal. Any ideas what might be causing this?. Thanks, Bob

 

does the idle come down when you come to a complete stop? is it only idling high when when you are costing down?

 

Is your vss plugged into the transmission?

 

When I come to a complete stop the idle stays high around 1000 rpm's. Sometimes when I come to a complete it will idle normal. It seems to idle fine when the engine is cool, but once it warms to operating temp. it won't idle down when I stop at a traffic light. Even if I hit the gas at a stop the idle won't come down. The transmission is a 5-speed manual. Thanks, Bob

 

Can you post your tune?