This seems to be a complicated issue which a new friend at the dealership thinks is software related rather than parts.
I have a 2003 Pontiac Vibe GT with 2ZZGE engine. This past weekend I cleaned the throttle body and IACV (idle air control valve). I did a complete throttle body removal and also removed the IACV from the throttle body. Everything went perfectly and was cleaned to new condition.
Exactly what I did: https://www.celicahobby.com/forums/u...rly-clean.html
PROBLEM: when I performed the clean I made sure to disconnect the negative terminal and I was disconnected for at least 4 hours (I was also replacing the oil pan gasket). When I finally started the car it idled at 2000 rpm. Once I actually drove it and then clutched to return to idle or put it in neutral the idle was 3000 rpm and a quick gas pedal flick would cause it to drop down and begin an idle search where it surges the rpm from 1500 - 2100. Sometimes this doesn't stop till I put it in gear and drive again or sometimes it finds idle at about 2000 rpm. I can also tell that while the vehicle is driving that there is throttle without my foot on the pedal.
I spoke with my new dealer friend and pulled my EFI fuse and relay for 1 hour with no change, so I left my car overnight with the EFI fuse pulled and still no change. I confirmed that when the surging is going on, that the throttle butterfly is fully closed and not moving. This means that the IACV is indeed working and is what's causing the surge. Like I said, the IACV is mechanically moving but it refuses to relearn proper idle.
The only thing I can find that is pretty much exactly what's going on with my car is this video were a guy has an MG that surges just like mine and he does a manual idle relearn through a pedal press/ignition on/off coded process. I've asked the dealership if there is a manual idle relearn override and they've advised that it's supposed to automatically relearn idle after ECM or EFI was not powered for at least 1 hour.
Just to be clear:
Throttle body is perfectly clean and butterfly is not restricted or not closing
TPS (throttle position sensor) was not adjusted or changed in anyway during cleaning
No engine codes or engine lights are present
Throttle cable is fine and tension is good