i own a 1993 trans am the engine has benn replace with a LT1 corvette engine ( year of corvette engine unknown) i took the car to the GM dealer in town to have it put on the computer and found i had a cut spark plugwire and needed rear brakes so i fixed those problems but my car is still acting up it is really hard to crank when it is cold and when it has been running for a while acouple of people told my to rebuild the throttle bodie so i went to buy a rebuild kit but noone around here has one so i ended up buy a new holley 52 mm throttle bodie same size as stock one. and replaced the throttle position and air idle control senors. but no the problem i am dumbfounded on what it can be but i love the car and i want to get it running right please give me ideas on what my be causing it everytime i go to put it in gear or even when it is in park it lopes one second it will be at 800 rpms then it will rise to 1200 by itself and when i am driving it i have to put it in neutral and keep the idle up when i come to stop lights or it will stall out. please give some information on what maybe causeing it.

 

could be battery or alternator?

you might want to post this on the LT1 forum.

 

Sounds like optispark problems my friend. Been there 6 different times with my last car.