[Terryd]

Hey guys/ladies.
First post here. Having some issues with an LS3/480 conversion. Hoping someone here might have had a similar issue.

A short background on the conversion. The engine is a new GM LS3/480. and the matching GMPP controller kit (harness, ecm, etc). I have a pretty good control wiring background so I felt confident in tailoring the harness to fit the application a bit better than it came out of the box.

First attempt to fire the engine: It lit off immediately, YAY! or so I thought. It was running terribly rough. Shut it down and performed the visual look over for something obvious. That is when I noticed that the header on the even bank was ice cold, odd bank was hot.

Since I modified the harness I suspected that I had made an error at some point in my wiring. To date I have run the pin outs 3 separate times. All checks out good. Tried re-firing several times with the same results.

I have checked for ignition power to the coils and injectors, good there too.
Put a Noid light on as well, shows the injector firing.

I managed to locate another harness and ECM. I overlayed the unmodified harness to confirm or deny that I had made a wiring error. Fired it up with the new harness...same result. Swapped the ECM...same result.

Anyone know of a scenario that would cause this?

Thanks and really enjoy this site! Very inspiring to say the least.

Terry