When I start my car and let it sit for a few minutes it idles ok. But the when it sits for more than a few minutes it's starts to idle high and then clicks and goes back to normal. why does it do this?

I have a 1985 Z28 with a 305 carb. engine, with only 114,000.

 

You might have a broken vacuum line, or something is plugging the carb.

 

See if the click is not the A/C compressor kicking on wich would cause the idle to go up it will do the same thing on defrost. If that is what it is doing how much is it going up?

 

I have a 1984 Z-28 and I have the same problem. When I start it the idle will go up between 20-25 sometimes as high as 30. Once it warms up to about 110 degrees it drops. I am not sure if that is the same problem you are having. I just let mine warm up and give it a little gas and then it is fine. Hope this helps.

 

Tiger the only thing that's wrong with yours is the choke "fast idle" is set too high. Should be right around 2k. Theres an adjustment screw on the side of the carb for it but on a Q-jet I'm not sure where it is.



Splitter....the whole thing is kind of confusing...I wanna say it's an IAC problem, but I don't even know if the Q-jet cars HAD an IAC (or similar mechanism). Take a close look at the carb one day and wait for it to do it....see if anything is pushing the carb linkage over and then releasing it. Thats all I can come up with.