96 1500 305 vortec popping/missing/etc

[SkysTheLimit]

Best bud has a 96 1500 5.0 that acting up lately. Start it, drive for a few minutes just fine. beat it, baby it, don't matter. Then, out of nowhere, it will start sputtering, popping, missing, falling on its face. Pull over, shut off, immediately start it again, drive for a few more minute just fine, repeat. Over and over. There does not appear to be a pattern or a catalyst to cause it to go nuts but it does appear to be more prone to do it at higher rpms (highway driving) opposed to in town. This may be just the fact that most test runs and driving duties are on the highway.

We've replaced wires, dizzy and plugs. When it's throwing its hissy fit, we can hear the fuel pump whining pretty loud (even over his glasspacks). Funny thing is, it's not throwing any codes. I'd be suspicious of the pump if it didn't work fine for a while. We sanded down the frame where the ground for the sending unit & pump is thinking maybe bad ground but still doing it.

Thoughts?

I was really purplexed when he had it scanned and got no codes out of it.

Any direction would be greatly appreciated.

 

[Xtremegmc80]

replace fuel filter??

 

[ryan22re]

Put a fuel pressure gauge on it.

That'd be a quick way to eliminate the fuel pump as the culprit.

Although the fuel pressure regulator could be leaking into the plenum. At least you could elminate the fuel pump with a gauge.

 

[bigblock72]

Check the fuel pressure when it acts up, could be the problem. If that turns out ok then check that distributor cap real close, or even replace it again even if you already have. Those distributor caps go bad and will arc from the coil to number 6 terminal and cause exactly what you describe. I've had 3 in a row do exactly the same thing and they were all good 40 plus dollar caps.

 

[SkysTheLimit]

He's going to bring it over to my house this weekend and we'll see what the fuel pressure is doing. What's the acceptable range on a 96 vortec? Is it the same as the older TBI trucks?

We'll check the rotor and cap carefully as well.

thanks!!

 

[ryan22re]

It's around 60 psi IIRC. Remember that it is before the fuel pressure regulator, it's more like 40-45 under the intake. I recommend hooking up a gauge and taping it to the windshield and driving around.

Also, check the "drains" in the dist for clogging. If the air can't move in and out of the dizzy, it can mess one up real quick. There should be one or two screens under the rotor. Maybe packed with dirt/debris. Clean with brake cleaner and light air pressure.

 

[Mudstud]

Head(s) cracked?

 

[SkysTheLimit]

More good advice. Thanks Ryan!

I don't think the heads are cracked, coolant was recently flushed and the oil was recently changed and no contamination was noted.

I did just dream up a cool outside temporary gauge mount... hard drive magnet (or any strong magnet) with a hose clamp jb welded to it.