Backfiring, Bucking and stumbling

[TwistedTahoe]

I've got a 1995 Chevrolet Tahoe 5.7L 4wd 4l60e and it backfires at any rpm. I started with the basics; fueling, timing spark, and found everything was in spec. I'll put together a list of new parts and their brands if I can recall them(Don't get mad at me for throwing parts at it, I had these all lying around)

O2 Sensor, Delphi fuel pump, Motorcraft fuel filter, air filter, ACDELCO spark plugs, ACDELCO spark plug wires, ACDELCO distributor cap, ACDELCO distributor rotor, Duralast ignition coil, Injector assy, reset timing to 00 as the catalyst said.

A Service engine soon light pops on while I'm driving but if I stop to check it, nothing happens. If I turn the vehicle off it just flashes all clear (1--2)

Injector assy - made a huge difference, before I did this the Tahoe was barely driveable, now I can at least run around town.
!!!ANY HELP IS WELCOME I'M ABOUT TO SCRAP THIS THING!!!

 

[Schurkey]

I've got a 1995 Chevrolet Tahoe 5.7L 4wd 4l60e and it backfires at any rpm.

1. Cranking compression test of all eight.
2. Leakdown test of "best and worst"--the highest- and lowest-pressure cylinders from the cranking compression test

Backfiring at all rpm is likely to be a non-sealing (burnt) valve. Another possibility is an exhaust valve that doesn't open.

I started with the basics; fueling, timing spark, and found everything was in spec. I'll put together a list of new parts and their brands if I can recall them(Don't get mad at me for throwing parts at it, I had these all lying around)

O2 Sensor, Delphi fuel pump, Motorcraft fuel filter, air filter, ACDELCO spark plugs, ACDELCO spark plug wires, ACDELCO distributor cap, ACDELCO distributor rotor, Duralast ignition coil, Injector assy,

What is the fuel pressure under load?

reset timing to 00 as the catalyst said.

Huh? My catalyst doesn't talk to me.

A Service engine soon light pops on while I'm driving but if I stop to check it, nothing happens. If I turn the vehicle off it just flashes all clear (1--2)

Stop counting flashes. Connect a real scan tool, find out what the computer is trying to tell you.

 

[TwistedTahoe]

1. Cranking compression test of all eight.
2. Leakdown test of "best and worst"--the highest- and lowest-pressure cylinders from the cranking compression test

Backfiring at all rpm is likely to be a non-sealing (burnt) valve. Another possibility is an exhaust valve that doesn't open.


What is the fuel pressure under load?



Huh? My catalyst doesn't talk to me.


Stop counting flashes. Connect a real scan tool, find out what the computer is trying to tell you.

Fixed the issue by totaling the thing.
Compression was 180-195 on all cylinders
Fuel Pressure was 8 psi
My catalyst does, weird. It's got a texan accent.
Real scan tool said o2 sensor. o2 sensor didn't help.

 

[PlayingWithTBI]

Fuel Pressure was 8 psi

That's way too low. Too bad you totaled it