intake backfire 1989 gmc 7.4 tbi

[panicx]

My truck runs great untell it warms up.
Then ( seems intermentent )starts to backfire through the tbi.

Things i had tryed ,
plugs,wires,cap rotor,reman dist.
The only code i ever got was for the tps,replaced it with no change.

any ideas ?

Kelly

[herefordman]

Sounds like still a timing issue, distributor in right and timed right ? maybe a bad coil ?

[panicx]

Well I did run the base timing up to 8 btc,calls for 4 btc.
But advancing it helped it not to backfire as much.
Set at 4 btc it will not hardly pull out of the driveway.

panicx

[herefordman]

Sounds to me like the distributor is worn out and moving around when it spins, missing the plug wire terminals occasionally when it fires.