Ttop86GT

I've been having problems with my idle since I got the car : at first, it wouldn't idle at all. I changed the throttle air bypass valve (idle air) and let the engine idle at around 1800 for 15 mins and cleared up some gunk (also stopped burning as much oil).
But now, with that, I need to rev my idle up to 1500 for a few minutes, and then it surges between 200-500 RPM. Lately, it's been doing that then dying after about 5 mins of idling rough. When I have it idling for about a minute at a constant RPM, the RPM jumps up a couple hundred by its own, with the TPS being in the same position.
Also, when I step on the gas, there's a lag before the engine revs up. If I step on it hard from a stand-still, the engine bogs down to about 50 RPM then climbs up.

Could it be the vacuum system, a cracked line or a way for the vacuum to escape? Or could it just need a thorough tune-up? Any help would be appreciated!

Ttop86GT

Bump

sm6989

I had pretty much the same problem, Cleaned the IAC and the MAF and ran excellent. But you said you changed out the idle air control, used one? clean it out before useing it?

Ttop86GT

I bought a brand new idle air, and I have a speed density sensor. I heard that resetting the computer's memory works better than letting the computer repogram itself for the new component.
I'm thinking it might be a vacuum problem though, because I put some thicker oil in, and it was surging and bogging worse than ever : maybe the vacuum isn't strong enough to clear up the molasses. I mean, Lucas oil :/