I just put a 2000 LS motor in my car on Tuesday. I have a 93 Civic DX Hatch. I am using the stock harness with a 95 LS ecu. There is something wrong with my idle. With the AC button switched to on, the motor seems to idle properly. But with the AC button turned off the car studders and dies. All in all it is revving up and down, up, down, up, down... and so on. The AC is not hooked up either. How can I fix this? HELP ME PLEASE. I am clueless.

 

check you timing sounds like its retarded cause when you hit the a/c button it ave. your timing and runs well