I have an 86 lb9 and it idles at just under 500 rpm. I can account for the tach being a little off, but it idles just low enough that the volts drop and the lights dim. It will also occasionaly die on me. It runs great, just idles too low. It had a recent tune-up and iac/tps are new. I set the minimum air and tps according to the tech articles on this site. It seems regardless of what i do, it will always idle at just below 500. I understand the 86's got a chip with the idle set 50 rpm lower than later years. What gives?

 

is it a tpi setup if so just give it a little more gas i think it should idle at around 750rpm

 

If its the tpi I would check the throttle body and clean it out. Check the air filter too. Also make sure the MAF is clean and is reading correctly.

 

My low idle problem was fixed when I started using premium instead of middle grade. It idles about 100 RPM higher now. Just a thought.