Hey guys I'm still troubleshooting my 90 Camaro 5.0 TBI, I've replaced the fuel lines and the fuel filter, plugs and wires, I still have an issue where it's idling at 1500 RPM, and when cold it surges up and down. Sometimes it will die out and sometimes it will keep itself running.. If the fuel pump isn't the issue, I have a feeling it's a vacuum leak, but i don't know what lines to check for cracks in. My question is what lines should I go after and what ones should I plug to test for vacuum?

Im no expert mechanic I'm 16 and this is my first car, I want to eliminate if te problem is a vacuum leak or not, hopefully this community can guide me in the right direction

 

I'm having a similar problem with my car. It starts fine but you can hear a 'soft' missfire. It settles down to a lumpy idle varying between 650 (normal) in drive and 1000rpm in N or P. She'll eventually throw code 35 (IAC 250rpm more than commanded for 45sec) But apart from that she run's sweet, it's driving me up the wall!

In your case I'd start with what I've already done, check the plugs, if they're mainly grey/white (lean mixture)then you probably got an air leak. Buy a can of carb cleaner (make sure it's safe for catalitic converters) and spray it round the intake manifold and any hoses that connect to it whilst the engine is running. Get into where the injectors go into the manifold and sprey there too, they sometimes leak in there. Also round where the throttle body joins to the manifold, don't drench the engine just light sprey's will do. Any leaks will show with a positive engine increase. That's the most likely cause of your high and erratic idle i'd guess.

Speed.

 

Maybe your tach is OFF--- i just bought a Craftsman tach- timing light and it shows that I have 575 rpm at idle but my dash tach shows 1100 rpm idle--- so my guess is that the dash tachs can be off- waaaaay off.