I just bought a 1991 Firebird and just put in a fuel injector rail, all new injectors, and a new fuel pump. When I push on the gas to take off from a stop at a decent rate or try to accelerate faster there is a popping noise, it isnt loud like a backfire and you cant feel it. Could this be a MAP or MAF sensor or more? Only thing I can think of would be exhaust or catalytic converter but I dont think thats the problem. The popping isnt loud like a backfire but more muffled like and I can feel it through my accelerator pedal.

 

Did you change spark plugs and wires yet?

 

It is either a MAP or MAF, car won't have both. 91 should be speed density(MAP). - sounds more like ignition to me. plugs/wires maybe timing advanced to far/module acting up...

 

Thanks for the reply guys, better and faster than other forums I've tried. Though I did find the problem...it was the exhaust manifold gaskets and a broken exhaust manifold bolt.