I have a 1988 5.7L gta. It was running decent, then sat for a while after I had a vaccum leak through the intake gaskets. After I started it back up the idle would either be around 500 or 1200 depending on how it was feeling that day. Eventually died on me while I was coming to a stop, and have to keep the engine revved up while coming to a stop in order to not stall. After it dies the starter repeatedly clicks like it has a dead battery, but with a meter it’s showing proper voltage. Jump pack will not start it but jumper cables will. It’s gotten worse and now it repeatedly dies out while idling. Replaced IAC which was very dirty, verified tps was reading properly, cleaned MAF sensor. When checking codes, one of two relays next to the radiator cap clicks erratically, and I hear what sounds like something motorized adjusting coming from the TB. Originally had a code for maf burn off and tps signal high. No new codes have popped up after reset, but while I’m checking codes it likes to flash the engine light erratically, which it also does when it’s running. Starter seems to be going out now as well. I’ve cleaned all the grounds I could find except the ones that go from the heads to firewall. Worried about it being a bad ecm at this point, if anyone could assist I’d appreciate it.

 

I also ran all new vaccum lines are smoke tested for vaccum leaks. Egr and Evap are both removed

 

The noise from the TB could be the IAC pintle stepping, trying to adjust. It would not normally do that, but with the diagnostic terminal at the ALDL grounded (for code scanning) it will run continuously trying to step the closed position.