Conversions & Hybrids - HELP!!!! engine running real bad

ok heres what i got, i got an '02 5.3 with a 98 LS1 ECM using the the painless wiring harness for an LS1, LS1 intake and injectors, fast fuel rails, aeromotive fuel pressure regulator. in an '87 trans am gta with a 700r4 ...

everything is hooked up except the exhaust (running open manifold), the o2's, the Vehicle speed sensor....

i just finished with almost everything, but today when i thought i would start it and see how it would do it cranked and idled for like 20secs high then it idled low as hell and ruff, it drops to almost turning off then it jumps up high and back down again.

if any one has any idea or experience and knows whyit may be doing this please help me and let me know.... thanks

It may be because the 02 sensors arent plugged in.

There are a few likely causes.

1.) did you reconfigure the '98 PCM to feed 5.3L engine? Injector size is definitely different in software, very likely there is a variable in there for cylinder displacement also. There was back in the '90-92 GM ECMs that ran speed density.

2.) wide open exhaust and disconnected sensors. Get everything hooked up, then troubleshoot if still necessary.



ok heres what i got, i got an '02 5.3 with the 98 painless wiring in an '87 trans am gta with a 700r4...

everything is hooked up except the exhaust (running open manifold), the o2's, the Vehicle speed sensor....

i just finished with almost everything, but today when i thought i would start it and see how it would do it cranked and idled for like 20secs high then it idled low as hell and ruff, it drops to almost turning off then it jumps up high and back down again.

if any one has any idea or experience and knows whyit may be doing this please help me and let me know.... thanks

any one else have any ideas or does every one more or less agree with what the other people suggested to be the problems