ive had this 86 TPI LB9 trans am for over a year now and it had a hesitation problem when i first got it. it didnt seem too serious at first. if you increase the throttle slowly it will spin up seemingly normally, but if i just crank it to WOT then the engine loses rpms for a second, then will spin up to redline and have a few stumbles along the way. ive replaced the maf, and the maf relays, replaced the timing set, and spark plugs. ive taken it to two seperate mechanics who couldnt figure it out, and it doesnt throw any codes...also when i first start it up after it has been sitting for a while and the engine is cold, but its not even necessarily cold outside, it will be hard to start, but when it does it will run like #$@% and slowly wind down until it stalls and dies. it starts easier after the first time, but sometimes it will still just wind down until it dies, i can keep it from doing this by revving it up a little, but it runs pretty rough and backfires...it runs a lot better once it is warm, but still has a huge hesitation. ive checked for vacuum leaks and checked the vacuum and fuel pressure, and changed the fuel filter also...everything was within specs...if anyone has experienced these symptoms or can offer me some help i would appreciate it a lot im about to just run it into a wall and call it quits.

 

Ive had some of the cold start problems that you have. one thing i did was check the TPS ( Throttle Position Sensor) turns out mine was bad, and way out of spec. I replaced it and also re-adjusted my idle. theres a tech article on how to do both of these in the tech section. anyway, i did this and now my water pump has went bad, so i havent really had a chance to see if it help a whole lot, but when i did drive it, it was running better. just a thought.

 

I had the same problem with my '86 TA, hard starts cold, manifold backfires, the whole bit. Once I got new injectors installed, the problem went away. One injector was clogged, and two had broken fountain tips under the pintle cap.

 

i believe another problem was the bugged prom in 1986 305 tpi cars

that can be it , i got a mint 27,000 mile trans am 305 tpi and it does the same when it is cold and starts

i need to get rid of that crappy bugged prom