i drive a 00 teg ls and just converted it to obd1. when i first start up the car it had a lumpy idle which eventually came to a steady idle(600ish rpm). i took the car out for a spin on the hwy and noticed when traveling around 5500 rpm's the needle will start to bounce from 5000-5750ish rpm's and when flooring it past 5500 rpm's the needle just slams down to 0 rpm's. ive tried two 0bd1 ecu's and they both do the same thing. whats wrong with this picture anybody else have this problem?

 

bump

 

do u have a aftermarket chip?

 

nope

 

Bad grounds. Check you thermostat housing ground, as well and engine ground, and also inspect your adapter harness carefully.

 

bump

 

Does it do this with the OBD2 setup? If yes....check your grounds on the engine. IF no, check the harness....probably a loose wire in there.

Jason