Just got car back from 355 LT4 conversion/rebuild.

PCMForLess programming was installed.

Car idled at 450 RPM & runs with a miss until it warmed up.

Mechanic insisted it was program so I reinstalled the stock programming & it still had the miss.

I reinstalled the LT4 programming again & car would only crank but not start at all.

I reinstalled the stock program again. Had to crank the car for a few minutes to get it to start . Once started, it still had the miss at 450 RPM until it warmed up.

Opti, Plugs, & Wires are new. Coil is original, but never gave any problems before rebuild. None of the wires are burned & they are not close to the headers.

WTF is wrong with this & what should I check? Fuel? Idle Controller? Something else?

EDIT: Car is a 95 Z/28 with OBD-I.

 

I would start with the simple things first,like a bad plug wire or plug.Probably new but they can still be bad.Check the fuel pressure?New injecters?New opti?Anyways work from there I am
sure its something Simple.Keep us posted,And good luck with it.

 

TTT...Anyone else? Car is going back to the shop today, I just want to be sure we don't miss anything.

 

To start with, your idle is way to low, find out why. Cold idle should be 900rpm +/-