does this sound like a vaccume leak, revs from like 2000 to like 800 rpm while at idle. it is a 96 ls motor, and i just swapped the intake mani for one off a 95 ls. i used a mr gasket intake mani gasket, and reused the gasket on the throttlebody. i have changed out the FITV and the IACV, still does the same thing. It idled fine before i changed the manifold.. I also put a different TB off a 95 on it since it has another vaccume port on it fot the charcole canister. When it idles up and down, it goes from like 14 psi of vaccume to 17-18psi of vaccume. im pretty sure this is a gasket leak, but i just need someone to verify my thoughts. I know i can spray come brake cleaner at the gaskets to find the leak, but i dont have any right now, and im stuck at the house because dumb family is here. thanks for any imput

 

Also, i just remembered, i changed all the stock sensors from the 96 manifold except for the IAT. Would that sensor cause it to idle like that??? its not throwin any codes, so i dont think its the problem. I also swapped the TPS sensor over, correct me if im wrong but its supposed to be .5 volts at closed thorottle, and 4.5 volts at WOT. One other thing, i have the 95 manifold ported out to accept a 64mm thorottle body, would that cause the problem??? i only have the stock 60mm on there right now though.

 

dont u hate asking questions that u know noone is going to respond to.

 

Spray some carb cleaner near the suspect gasket and see if it speeds up (with the engine running) if it does then you have a leak. I dident know you could swap TPS sensors since they were calibrated to the thorttle body. Maby thats just other cars.

 

ok, i found the problem, u cant use a 96 ls tb gasket on a 95 ls manifold. The 95 has the FITV on the bottom of the throttlebody, but the 96 doesnt. So, the 96 gasket was like a 1/4 inch short at the bottom, and air was leaking there. Made a gasket out of a folder, and put it on and runs perfect now. I know, the gasket is kinda bootleg, but it works.