Expert: Grip Singh - 9/7/2006

Question

i have a 1978 chevy K20 with an 1988 350 that when the motor warms up and u drive it it back fires and wants to shut off intill u let off the gas?...when its cold it runs great...can anyone help me out..asap!!!!

Answer
Sounds like its fine in open loop but in closed loop it runs like crap.

That means one of the sensors is telling the motor to dump more fuel in which burns in your exhaust causing the backfiring.

When was the last time you changed the O2 sensors? Does your truck have a MAF sensor? If so, clean the screen or swap in someone else's to see if it makes a difference.