mvvette97

Hey guys I need some help with this car. I just bought it all torn in pieced. It's a 94 Z28. I put a new stock engine in it and it idles rough and and kinda hunts up and down for the idle. When I just give it a quick rev it will pop back in the intake from time to time also. I adjusted all the valves so that's all good. It will start and after about 10 seconds the check engine light will come on and stay on. We tried to read the codes but when we plug the code reader in it says it has no codes. How can this be when the CK engine light is on. I can't figure this thing out for the life of me. What should I start with now?

Injuneer

What kind of scanner are you trying to use? You can't use the $30 Actron scanner, because all it does is short the pins on the ALDL connector to flash the codes on the SES light, and that will only work on the 93, not the 94 and newer.

Who assembled the "new stock engine"? Is it possible the Opti was not indexed correctly?

mvvette97

that may be what he has for a scanner. He said it was a cheapo. The engine was assembled other than the opti and I put that on myself. What do you mean by not having it indexed? I could only see one way it could go on. It had a little flat spot on the splines on both ends of the little shaft.

lt170chevelle

Check your plug wires. I accidently crossed two wires when changing plugs and it idled rough and would pop thru the intake.

mvvette97

I checked that but they are all fine. I have a friend coming in the morning to try to scan it. He has one of those new Snapon scanners so maybe he will be able to tell what's wrong

Injuneer

It may appear that the odd "tooth" on the Opti drive shaft will only go together one way, but unfortunately about 10-15% of the installs manage to go wrong.

If the new Snap-On scanner has OBD-I capabilities, it should be able to scan your PCM.

mvvette97

yea I'm not sure how somebody could get it wrong. I had some trouble getting it to line up but you can tell easily if it's wrong. I know what you mean though, some people force things togethor