4.3L runs like crap.....Help

[agood1]

I just aquired a 93 GMC sierra pickup wih the 4.3L V6. I know this engine has about 30k miles on it as the previous owner had a crate motor put in a year or so ago.

But is now running terribly, There is at least one cylinder that is not firing....but I can feel it hit every now and then. The idle is rough and the acceleration is poor. I even backfires every now and then while accelerating.

I have done the basic tune up...plugs, wires, cap and rotor.....and that did not affect it at all....

I don't want to chase this with parts...but I don'e have access to much diagnostic equipment.

What could it be? I did a compression test and all cylinders were OK.

Dist module?

Fuel filter or pressure?

Bad injector...

 

Where should I start?

 

Thanks.

[drumset5994]

Timing?

[lab1508]

How do you set the time? What lines up where?

[redvett]

Unhook the tan wire at the buss bar above the heater and set timing according to the sticker on the rad support or shroud. Probably around zero degrees.

[HyperBuzzin]

I have a '00 Jimmy that's running pretty much how you described, except for the backfire.

I'm pretty sure on mine, it's a bad O2 sensor.