90 firebird, random studdering and stalling?

i have a 90 firebird bandit II, just a regular old formula. it has a newly rebuilt 305, tbi. car runs great for the most part, but it randomly starts shaking, studdering, and then just stalls out, and im left to pull off the road and it usually wont start again for a good 5 min. i replaced the pcv valve, i know that would be the last thing to go bad, but it was 3 bucks and i fugred why not?. but that didnt help. when it acts up i can get it to go a bit, but it has now power whatsoever, and i get a slight burning smell from the heat/ac. i can get the car up to about 30 fine when it does this, it takes a while, and it sounds like a lawn mower in doing so. if i knock it into nuetral and rev it up a bit it'll be fine for a while. the motor i believe is from a 92 camaro, but same motor reguardless. original motor blew when my uncle hit a pipe of some sort and either knocked off or cracked the oil pan. i have a code scanner and it says there is nothing wrong with the car. the car does not have the cover on the air cleaner assembly like all the other 3rd gen tbi's, and has an aftermarket air filter, and the cowl induction hood. could moisture or water get in through the hood and into the exposed air filter? ive takin it numerous places and no one can figure out what is wrong with the car. the tbi was replaced but it still does it. anyone have any ideas? please help! thanks

Does the check engine light ever get triggered and have you checked fuel pressure?. I think its ignition related though from the way it sounds to me you have a burned up spark plug wire or fouled plugs but could be a great many things. Good Luck

John

Welcome to the forum

i can be many things do a compression test on all cylinders they should be no more than 30% apart. if they are good then disconnect the y-pipe and start it to see if the exhaust or cats are clogged. if those don't work try to check the resistance on the ignition coil and check the distributor for carbon tracing. It sounds as if something is expanding and resticting the flow in the paarticular area causing it to choke on itself. Good luck and Welcome to the Forum

sounds like you need to do a tune up. try replacing the plugs, wires, dist. cap, rotor button. and change the fuel filter, and dump a bottle of feul system cleaner in the tank. good luck

hey thanks for the help, i've narrowed it down to two causes. either a loost baffle in the muffler is blocking exhaust or most likely the cay is claugged. the car started doing it when i pulled in my garage, so i got out a popped the hood and heard a loud hissing, and there was exhaust pouring out of the header gaskets, so something is claugged somewhere. i was thinkin cat but that would be claugged all the time, and the muffler is a bit old so maybe one of the baffles is loose and sometimes rattles around and winds up blocking the flow maybe? ive got ahold of a "test pipe" for the car so im gonna pick it up from a friend and put it on in place of the cat and see if it solves my problem,and if so ill just buy a new high flow cat, cause its kida stupid to have headers with the stock cat anyways. and i did just do a tune up probably 300 miles ago, and a new/rebuilt motor was dropped in the car less then 20 thousand miles ago so everything such as plugs, wires, distributer cap and everything else should be in decent shape. thanks for the help!

cats are common causes of these problems they do work when they are cold but they operate at around 700 f and when they get that hot the carbon expands and closes it off a tale tell sign of this but not always is when you shut it off it sounds like a thump almost a backfire from the engine when the built up pressure runs back through the open vavle and out the intake