96 chevy k1500
 

i dont know if im allowed to ask a question about a non f-bod, (if not feel free to delete this, mods), but you guys are the most reliable source of info ive found about this stuff.

anyway, my dad has a 96 k1500 and its got the 350 vortec. a few years ago, it backfired and hasnt run right since. hes replaced the longblock, injectors, map sensor, tps, plug wires, plugs, cam positioning sensor, knock sensor, iat sensor, egr valve, pcv valve, trans, and o2 sensors. and it still runs like crap. it has a rough idle, accelerates with a lot of stuttering then cleans out at high RPMs. like its choking itself out all of the time. hes had it to a few shops and they have nothing to say... any suggestions or has anyone run into this before? we're thinking maybe computer? it had a ses light on until i ran a can of seafoam through it.

again, sorry its not an f bod, but i gotta figure this one out

clogged cat or the timeing is off or a bad injector

He did all that to chase a rough running condition @ low RPM which didn't start until some sort of backfire?

- Justin

my 90 gmc did something like that and we took apart the TB and under the injectors it was totally clogged with dirt ??????????? i replaced it with ajunk yard unit and it ran great again <<<< maybe it something like that guessing - jz

A '96 Vortec motor would be SFI, not TBI, wouldn't it?

- Justin

It's kinda both SFI and TBI....there's one central injector that runs to individual poppet valves. If that's been replaced as well as everything else I would suggest taking it to a GM dealership and have them check the timing with a Tech II scanner. The phasing with the camshaft position sensor can only be set with a Tech II, a timing light will not work on these engines.

Paul, is that central unit similar to the ones that were on the 6 cyl, like on the trailblazers? I remember them being problematic. They'd go bad and drop a few psi, just enough to make them hard start & idel weird.

he got it timed at a shop and didnt help. well look into that central injector thing. that would just be a fuel pressure regulator woudnt it?...or does it have a timed spray? yes tru2chevy, all this because of a backfiring problem. it started backfiring and he immediately replaced the plugs and wires. it never backfired again. after that it never ran right again. could it be the ecm or would that have different symptoms?

Yes this is the setup. They sell an upgraded version with metal poppet valves that's much better than the factory unit. Been running one in my truck for about 60k now.

I remember them being very finicky. Like the book calls for some ridiculous (at least at the time) fuel psi, like 60+ psi, and these things would go bad and drop the psi to like 51 psi and the damn things got all goofy. Close was not good enough with those setups.

check the distributor cap... They are very problimatic espically in damp weather...