OK i got and idle problem and I have searched like crazy trying to figure this out now I got a 1980 cali 20r my problem is when I start it cold or hot it will run at 1000 to 900 rpms for about a minute then drops and jumps between 300 and 500 rpms it drives good down the road non smoke no missing but right when I stop to idle it drops back down and starts jump from 300 to 500 I've put new carb timing is dead on 8degrees adjusted the valves all vacuum lines are good and in there correct spots new wires new plugs does have a small exhaust leek gonna fix the today what else could it be

 

If it drives fine otherwise, I would just crack open the throttle a bit more at idle.

 

Not too familiar with carbs, but is there a stop screw that is there to stop the throttle lever when you arent on the gas? Maybe adjust it out some...

 

Yeah iv tried adjusting idle screw it won't hold at 800 rpms it either goes to 1000 or bounces around 300 to 500 it doesn't bother me to bad but I don't think it will pass cali smog if it can't hold correct idle I just fix the exhaust leak didn't help idle but sounds better ha I forgot to mention I have replaced pcv earlier some times Iget a small backfire out of exhaust about 15 sec after I turn it off

 

Sounds like its to rich if it backfires after turning the engine off (dieseling). Readjust your fuel and air mixture screws and idle should change as well. Try backing down the fuel mixture a 1/4 turn at a time until you get it right, or depending on where the fuel mixture is open the airflow a bit to lean in out.

 

OK I got the idle down with adjusting the the air mixture a bit but it still sounds like it's not firing good on one of the cylinders I pulled the plug wires one by one to see if it was a dead cylinder and there all firing so I pull the dissy cap and notice that theres a chip in one of the signal rotor gear teeth would that cause a low spark in wine of the cylinder?

 

Here a pic of the chip.

 

No one?

 

maybe. could be possible. i could explain why at idle it is more noticeable than while driving. try swap the dizzy and see if it goes away.

u have the OEM carb or aftermarket?
1lowSr5 sounds like a plan. try adjusting the jets.
a good tool to have is an AF meter. it would be easier to "tune" ur air/fuel