I need some help with my idle on a freshly built LT4 w/ cc503 and full bolt ons. I have a really rough idle that cant idle below 1100 or else the car shakes bad. Using freescan I noticed that my IAC count during idle is 0. I believe this is my issue but how do I go about fixing it? The throttle body is a proffesional products 52mm.

 

Try backing the throttle screw out slowly until you get IAC counts around 30

 

I know if I try to back it out the motor wont have enough Rpms to idle and will just die.

 

ice...

you will need the pcm tuned for your new cam set up. motor won't idle with a cam swap on stock tune.

the tb is another issue which also needs to be adjusted. IAC counts want to be 32 (30-35) with engine at operating temp.. Typically aftermarket TB's max out IAC IIRC at 160 so 'opening" the blades VERY slightly is a way to do it but typically in doing the open blade thing the TPS volts are off. You can do the "slot" the screw holes on TPS but IMHO the "drill mod" is the way to go.

Drill mod involves drilling the hole between blades as stock TB has it. Start with 1/8" hole and go up 1/64" until IAC is right. Take BABY steps as each 1/64" bigger makes a big difference. 11/64" -13/64" is where many wind up but DO NOT just drill a hole that big. Start with 1/8" and check each time while scaning TPS & IAC.

 

Good info, I did have the PCM tuned for my setup by Solomon. What should the tps voltage be at idle? I wonder if the idle is really sensitive to tps voltage, when I checked it was at .59v at idle.

 

It's going to be around .57 to .67 until u move the screw on the TB then the tps volts will change then you will have to adjust it