I am running a quadrajet carb. When I set the idle speed to 850 runs fine. After a drive and the engine heats up to say 220 if i put the car in Park the idle will be up over 1000. The choke plate is completely open and the high idle cam follower is not on the high idle cam. The curb idle is resting on the adjustment screw. What do you think this could be? I have checked for vacuum leaks but maybe it only leaks after it get hot? This is a TPI conversion so I am still running the stock pump with the holley regulator but I am using the stock return line. My fuel pump is at 7psi cool but I think the PSI is around 8 after the engine heats up. Maybe this is causing the idle to go up. What are your thoughts?

 

I set my desired idle at fully warmed up, like driven for 15 or more minutes.

I have a manual choke (blades removed, but high idle still works.) I use this upon startup, let it warm up, and turn it off once rolling and fully warm.

Basically saying I think this is normal, but when cold you have a solution to raising your idle (choke/ high idle)

 

Your oil thins out when it gets warm so the idle goes up from less resistance to the oil flow. Set your idle hot.

 

Thanks for the advice. Screamin82 Z28, I did set the idle back to 850 when I got home yesterday while it was as hot as it gets. Today I started it up and let it run at the high idle longer than I normally do to get a little more heat in it then kicked it down and it was right around 850. Drove it till it was hot and idle was still good. Thanks for the help. Bird91ZRAG thanks for the advice.