This truck is on my last nerve

[DaFuzzy]

Hey y'all,

Always came here to look up info, it's a great source of it! Anywho, background info it's a 93 k1500 5.7 tbi, 3.73 gears, 4l60 trans.

Bought the truck new to me about 9 months ago and it always ran okay, not great but meh.

My problem started after I got an exhaust put on. Was driving it home and it would pop and sputter under acceleration, definitely not normal, and finally limped it home assuming it was a fuel pump going out or something. Once home I parked it and tried to start it the next day and nothing, nada... just gurgles and sputters. That was probably 6 months ago.

So I had some general maintenance and updates I wanted to do on it anyway for my piece of mind. Swapped in a new mild cam (dot to dot, rotated til both at 12), and a new distributer, plugs, wires, cap, fuel filter, pump, tank and lines.

I ran a compression test and all 8 fall into 130, 140 psi range, fuel is getting 13 psi, all 8 cylinders have spark based off inline tester, and my noid light shows passenger side injector has great pulse the drivers side has it but it's not as well lit or defined, both sides spray. I've unhooked the headers in case they were blocked, checked grounds, I even tried swapping out a good ecm in case the exhaust shop didn't pull a battery cable and fried the original... still no luck, still burbles, gurgles and almost wants to fire just wont.

I've done everything I've ever known to try and I'm not new to the shade tree mechanic world... I'm truly at a loss now though and was curious if anyone on here has any insight they could provide me... besides just pushing the thing into the river

Thanks for reading that long winded post and for any help!

 

[skylark]

Unhook one injector and try to fire it. If the coolant temperature sensor has failed it will show minus 40 degrees. If it fires on one injector and then it is running too rich. I typically like to see 150 or better for compression as well. Did you do that compression check before the cam or after the cam?

 

[DaFuzzy]

Thanks,
I will try unhooking it when I get home today, as far as the test it was after the new cam.

 

[wheelman]

Maybe a computer problems.did you disconnect battery and reset the computer.

 

[CrustyJunker]

If you have no check engine light, and started running poor after exhaust work, that almost sounds like it could be O2 sensor related. Not necessarily that the O2 is bad, but if it's scavenging air in somewhere nearby (manifold gasket leak, collector gasket leak, pinholes near O2 bung) it can read off and cause it to run poor. That shouldn't have an effect until after it goes into closed loop, though.

You also mentioned a cam swap. What did you set your initial timing to? My cammed TBI trucks wouldn't run at 0° like factory recommends.

 

[skylark]

Thanks,
I will try unhooking it when I get home today, as far as the test it was after the new cam.

The lower compression could easily be from more duration of the cam. It could also have a lack of vacuum with a larger duration. A low vacuum signal will make it run like crap now but it wouldn't explain the before.

 

[eyesi]

plus to all help suggested here, i would add to check PCV system, not only the valve but expect for a strong vacuum at base of tb pcv vacuum port

 

[DaFuzzy]

Sorry for the late reply, didn't get out to check it til today.

I unhooked drivers injector and tried to start, then hooked it back up and unhooked the passenger side and tried... no luck. My temp gauge never budged in the truck at all, maybe a quiver if anything.

I have unhooked the battery and hooked it back up to swap the new computer and then to swap the original back in later.

I'd set the cam back in at 0, that could be part of the problem now, as it seems to want to fire... just never can.

Yea, I kind of wish I'd taken a compression test before I swapped the cam over, I had assumed it'd be something simple. The old adage about assumptions still stands strong with me

I will certainly check out the pcv, ports, and vacuum hoses.

I appreciate all the help!

 

[Hipster]

It never fired? possible the distributor is in 180 out? Just asking. The balancer comes past zero twice. The spitting and sputtering erratic spark is pretty classic for an ignition module.

 

[thunderstruck]

Did you check or replace the ignition coil?