To start off I have a 04 Intimidator SS Monte Carlo SS. I have done some upgrades, a flashed PCM from ZZP, a TB 1" spacer, Thrasher CAI, HID headlights, and a Power log. Living in Cali, I had to take all the after market stuff off and return it to OEM for smog test. Replaced everything to OEM except the PCM. At first the idle was to high, having a OBD II hand held, it gave the DTC for IAC, so I replaced that and passed smog. Then everything started changing. Upon start up my dome light would be dim and will get brighter when I would press the gas pedal. Then a got a DTC saying idle was to low, so I replaced the IAC again. Having the original alternator I replaced it and replaced the PVC value and gasket. I only use full synthetic oil, Total 5W30, and 91 octane gas. I have since put back on the spacer, CAI, and have taken off the HID lights. Sometimes it will not even start when I turn the key and stalls out unless I give it gas and have it at 2k rpm, or when coming to a stop it will shake and shutter, once it stalled with the RPM gauge down to 500. I have read multiple things of what it could be...the ERG value, ECT, Timing belt, MAF, and a few other things. So I am opening to get some answers from fellow Monte gear heads to help me out. I do not want to keep replacing things and hope, I would just want to know what it is so I can fix it once and for all. Thank you for your help!!

 

Still honestly sounds like your IAC is bad.

Though you should also take a look at your MAF. Can you disconnect it the next time the car starts acting up, and see if you can start it then??

What kind of filter are you running for your CAI? If it's an oiled one, you could have too much oil on it and it go on the MAF, ruining it. They are very sensitive.