I have a Texas Speed built LS3 in my 69 Firebird track-street car. I have a lot of track and street miles on it. Last fall I had an issue with a coil going bad. I replaced it with a AC Delco (what Texas Speed had sent with the motor) and all seemed well. I don;t have a "Check Engine" light on and have driven the car since. It just seems like the idle is a little different. Maybe I'm imagining things. I was wondering if it could be a fuel injector issue on one of the cylinders...or something else I should check in to. Thanks for any input!

 

Start with a plug read and a data log.

 

unplug and replug them one at a time while idling and see if the idle changes, if you unplug one and nothing happens youve found the bad one

 

Another idea, fuel injection cleaners have become affordable. They do flow tests which would show what injector(s) is underperforming.


I bought one and found several injectors needed cleaning after a simple flow test.