So I just finished installing my subframe minus the rack & pinion bolts(forgot about those), it took me three days simply due to how rusty my bolts were. Once everything was loosened it went fast, I had to remove my exhaust from the manifold to make room as well as during the entire time I left the battery unhooked as I saw on here in a few threads doing so is safety thing. I just reconnected it and hooked my iat to my intake (had to make a hole for It in the intake).

At first the car was smoking on from the manifold roughly about 1 minute but stopped then after turning the car off and on a few times (had to tighten the manifold bolts to cease the smoking) the rpms began jumping from 1000-1500 sometimes up to 2k. I checked for vaccum leaks, throttle cable, o2 sensor, I have no idea why it's doing this. I had before this a exhaust leak near my cat but it's never done this. My abs cord on drivers side got cut off when my control arm brace snapped. So much abs light is on but that wouldn't cause it would it?

I have a manzo header/downpipe that I intend to install I just can't get the downpipe on without cutting thee pipe and I lack pipe cutters or a welder.

Anyyays any ideas guys?

Well I took an hour walk last night then started her up and no rpm jumping albeit staying steady at 12-1300 rpms. My norm is about 1-11k so just a few moments ago I started her up again and everything was fine. However when began warming up the jumping returned. Is my Iacv bad? I have an obd2 scanner on the way but what do you guys think? What else could it be?

Sometimes it just takes a while for the computer to re-calibrate itself after the power has been disconnected. After a few cycles, it should be normal.

It does sound like a vacuum leak. Im assuming you remove the intake manifold to relocate the IAT sensor. The IAC may cause that & I try to blame mine for everything. Mostly cause its easy to get to on an Ecotec, but its always been OK. It could be the O-rings/gaskets on the intake or throttle body are out of place. Id remove the intake manifold & re-check everything there.

How is the MAP sensor?

Or it could be the computer just needs to re-calibrate itself as Steve said however I have not had this kind of issue from leaving the battery disconnected.

The Iat is new and I haven't relocated it unless creating a socket for it to.fit into my intake counts. However I believe I found the culprit, just a few cm before my flex pipe I noticed a good portion of air just wooshing out plus the hissing. Why it Is just now now noticeable I'm not sure but that has to be the culprit. I have a manzo header/down pipe so will installing it without adding a flex pipe be a bad idea? I have the prothane upper insert & lower torque strut swell as a new tranny mount. I know what the fldxpipe does but with my mounts will it be nescessary?

So lil update, header/downpipe installed and fastened securely however my 02 sensor broke so currently have no pre-cat o2. Did an oil change with RP high milage full synthetic 5w30 and a RP filter as well as new NGK platnium spark plugs gapped at .60 annnd a new pcv valve. I removed cruise control and my a/c compresser using a smaller belt and with all that still my rpms jump the same as they have been. So if my o2 isnt the culprit upon getting it fixed what else could it be?

IACV? Timing chain? fuel pump? Come wed I will be doing a trans fluid/filter change with RP max atf which is also syn. I also put my 205/55/16s on but that shouldnt contribute to the rpms jumping