backfiring 454

[bigjimdaddy]

I have an 88 sub 3/4 ton 454 2wd 400 turbo when i tow on the highway it will start to backfire though throttle body does this for 10 to 15 seconds then stops truck runs fine again . then ten to fifteen miles down the road it will do it again . it really makes me and my wife nervous be cause we start to think its gonna leave us stranded along side the road with kids and camper waiting for a tow truck. it has never died just backfires though throttlebody. I have hooked up code reader and it comes back with no fault codes. took it to local shop and 200 bucks and a week at the shop they said we dont know . Even hooked up camper and took mechanic for a drive . he just got an extended break cause it didnt do it. If anyone has any ideas I would love to hear them . love my truck and dont want to lose it. wife says she doesnt trust it, and wants to get rid of it . so please help me keep my truck

[G.A.S.]

when is the last time you did a full tune-up?
cap, rotor, plugs/wires,fuel filter,air filter,pcv valve ect.

[bigjimdaddy]

plugs,wires,cap,rotor,and air filter,all changed last summer. but this truck is only driven about 3000 or less miles a year and was backfiring though throttlebody before this was done. only does this when towing

[G.A.S.]

Try this.
There is an EGR valve to the left of the throtel body. Unplug the vacume hose, plug both ends . A Plug in the vacume line and a cap on the EGR's stem.
This isolates that valve.
I have an 88 gmc and now that I am thinking about it I had that simular problem 10 or so years ago.
Disconected the EGR and the problem was gone.
Mabey give it a try.
It wont hurt the engine to run with the EGR disconnected temporaraly.

[bigjimdaddy]

ok i'll give that a try .thanks

[bndfishing]

Pull the distributor and check the condition of the gears and bushings.

[bigjimdaddy]

I changed fuel filter again runs great again just got back from 200 mile trip towing a camper , not a single problem so thanx to all that replied, i read many threads on this site and found one that described the same symptems my truck had they called it lean popping . i guess from low fuel flow though a dirty filter.