I have a 90 rs with the lo3 v8. I just put in a 91 305 caprice engine and replaced all the sensors, plugs, wires, etc.. It ran but not very well at all. So I started digging in and found out that the hose that hooks the pump onto the sending unit was shot so I replaced it. I also rebuilt the throttle body but nothing seems to fix my problem. Now the car fires right up and purs like a kitten but if I take her out on the road and mash the throttle it bogs, and sounds like its holding back bad. It runs great if I baby her up into the rpms, but if I get to heavy with the pedal it just runs like crap. Any Ideas?

 

Sounds to me like a bad Throttle Position Sensor. But I think that would be throwing a code. Are you sure the ignition timing was re-set correctly? And did you re-connect the black and tan wire afterward?

 

When i set the timing i unhooked the black and tan wire, set it to 4 degrees advanced and hooked the wire back up. I figured that the idle would surge if the tps was bad.

 

The idle doesn't depend on the TPS, if I understand it correctly. The TPS is more like the accelerator pump of a carburetor.

 

You are correct sir. I was confusing the tps with the iac.