When I first start my car is has an idle of about 750 rpm. After it idles approximately 2 minutes, the idle goes up to about 1200 rpm and won't come back down. It was suggested earlier that it may be either a vacuum leak or IAC. The IAC was replaced with a new one a few months ago as was all the TPI gaskets. Any other ideas?

this is when you get out the good 'ol WD40 and start spraying around to see if you have a vacuum leak...you'll know. You start spraying around your vacuum hoses and all the sudden your engine will surge. (= vacuum leak) If not, then it could be a relay, could be MAF, Could be a lot of things. Are you throwing any codes? Doesn't actually matter. What year is the car, what engine, etc. If it's a computer thing, it could be a lot of things. Gotta know these things first. Sorry to be so ambiguous. My particular problem was MAF and O2. We need for for your car.m Help us out.

The car isn't throwing any codes at all. It's as if the idle is completely reversed. 750 rpm idle on startup, almost exactly 2 minutes later it will idle up automatically to about 1200 rpm and remain there. The "idle screw" is backed completely out. It will also surge a bit at a stoplight slightly bit nothing drastic. I am looking to get the stuff to read and burn chips from Craig Moates but haven't done so yet. I'll recheck for a vacuum leak...again.

Engine is a 383 with AFR 190 heads, Comp Cams hyd roller cam 218/224 .495/.502 112LSA (basically LT4 HotCam), Hedman shorty headers with dual cats, 1.5 roller rockers,

89 WC T5...soon to be replaced with retro-fit T56

'87 TPI with descreened and definned MAF, TPIS base with SLP runners, plenum and runners ported, TPIS Level V chip, new EGR valve, new IAC motor and housing, new 24# injectors, base and runners resealed when the injectors were installed, all emissions retained, stock throttle body with TPIS airfoil, ...

Can't think of anything more as of now...probably will after I send this.

Any other ideas I sure would appreciate it. I'm looking to buy a Super Ram plenum and runners (to remain emission legal) very soon and start burning my own chips and I'd kinda like to has this resolved by then.

Do you have the cold start injector? Honestly, I don't think you're supposed to have the screw on the tb backed all the way out. You could do the resistor check. I'm not exactly sure what resistor size to buy, but you plug it into the CTS and it tricks the computer into thinking that the engine is still cold. Then it tries to compensate by dumping more fuel into the engine to warm it up (ie cold start). You should try that once the engine is up near 1200 rpms and see if it drops back down to 750. DO NOT leave the resistor on there for long though cause your temp will keep going up and burn up your engine. That is a little trick some people use at the track to get better ET's just so you know.

I've heard of that trick. If I'm not mistaken, it's something like a 640 ohm resistor.

Yeah, I have the cold start injector but I can't honestly tell if it's working or not. I also have had problems trying to adjust the IAC the way it's supposed to be adjusted. I hate not beening able to see what values the ecm is showing...I'm working on getting the stuff to do that. Nobody around here does this sort of thing that I know of. When I tell them my TPI and engine is modified, they freak out and don't want to touch it

This setup was bought used and transplanted into my Olds Cutlass using a Howell emission harness. My dual electric fans and seperate from the computer and controlled independently.