1994 sonoma 4.3 vortex backfires around 2500 rpm

[bill4fun]

My truck started to back fire through the tbi about 2 weeks ago during acceleration around 2500 rpm. It backfires until you let off the gas. If you hold the pedal down it will keep backfiring until the engine tries to idle at 400 rpm. You have to turn it off and then it starts fine but will backfire around 2500rpm again. I have replaced the fuel pump, fuel filter, air filter, plugs, wires, cap and rotor, coil, both injectors, overhauled tbi with new gaskets, idle air control valve, checked egr valve by hooking vacum line direct to egr and piston worked and engine started to miss under vacum. I have checked disturbiter cap for correct timing. Engine doesn't have a miss or rough idle. Runs fine till you push the rpms up. Only 100,000 miles on engine with a new rebuild trans. Any ideas would be appreciated. I don't have a cat of muffler on the truck. The problem lies in fuel not being burnt. It is either timing or fuel itself. I changed feul regulator in the tbi and no change either. Even used transmisson fluid through the intake to burn off carbon on valves. Any ideas would be helpful.

[Blaze_x]

Any SES codes? It sounds to low of mileage to have a timing chain problem but it would be possible. Have you watched timing at 2500rpm when it backfires? Also a TBI 4.3 is not referred to as a vortex.

[Slacker1357]

you running regular 87?
hows your exhaust?
would a clogged cat cause any of this?

just throwin some ideas out there...

[bill4fun]

There are no codes. My truck was produced with the vortex heads. It is stamped on the valve covers. I replaced the intake manifold gasket one time and they said the same thing but when I brought the gasket in to match, it was the vortex. I wish there was a code.

[bill4fun]

I am running 87, never had any problems with it before. I also thought of a clogged muffler and converter, so I cut them off and ran striaght pipe.

[TreasonAgainstCaesar]

I think you're trying to say Vortec. Sorry, that's all the advice I have.

[spideyjected]

TB needs a rebuild? ign module? distributor? pick up coil?

[bill4fun]

I will try to rebuild the componets to the dist. Thanks

[XTREME80]

Sounds kinda like ignition or timing related, Maybe.

[vmss10]

I would start with looking at the dist. cap or ignition module. Definitely sounds spark related.

[bill4fun]

Thanks to everyone that gave me advice. I changed out the ignition control module. It boosted up my power and stopped the backfiring. The module was getting hot and would short out from time to time. Thanks again!

[Junksterr]

glads we could help even tho I didnt throw any opinions out there... glad ya got it fixed....

[TreasonAgainstCaesar]

NICE!!

Did you use an OEM module?

[bill4fun]

Went to autozone and bought one for around 40.00

[BigTruckDrivah]

Good luck with autozones junk modules

[Jongo88]

Good luck with autozones junk modules
You need lots of luck!!!


That's no lie.
A big X2!!!

[XTREME80]

X3! I would have bought a Delco unit. IMO just a thought. Glad you got it running though:D




Off topic, back to swimming pool maintenance.