well for the basics, i have a turboed gsr and ever since i have been tuned on s300 my car ran great for a week or so and randomly it started throwing the codes for the IACV and the Map sensor(aem 3.5 bar). After another week or so of driving, the codes randomly went away for a few days and i took it to the track where the code for the IACV came on again. The other odd thing is, the needle for the tach jumps around and shortly after is when it throws the code again... when the code comes on if i let off the gas the needle goes to 0 and the car actually stalls but if i put my foot back on the gas, it drives fine. When it threw the code at the track i replaced the IACV with another and it was fine untill the next pass where it the CEL came on while slowing down. The next day the CEL didnt come on until 2 hours into my road trip... i really have no clue what the problem is and any advice would be greatly appreciated... also sorry about the length of the post..
Jeff

 

anyone?

 

have you checked your grounds,,,,at the thermostat housing and battery?

 

yes all grounds are fine...

 

this is driving me crazy

 

Do you have engine mounts? Kinda sounds like wires, or wire, is shorting out. Possibly as you lift and the eningine shifts, or who knows.

I once had a problem where my car would randomly, or i thought randomly run like crap. This was a cavalier z24, but what was happening was there was this harness that ran by my ac pump. When it was off, it wouldn't spin and the wires were fine, but if i turned it on, clutch engages, and then the wires were getting shorted out, little electircal tape, and zip ties, and problem solved. As random as your problem is, i'd look into something like that, specialy since you replaced the part.

 

yes i was thinking that could be the only explanation, but i dont even know where to begin to look... also the needle sometimes jumps even with no check engine light being on.... and i have my two tq mounts and the driver side mount filled with window weld...