95 6.5l 2500 GMC - Fuel Problems

[Phantomz]

So a few months ago my dad was out driving this using it as a work truck and the fuel started sticking kinda and was real weird. After that day we started the truck twice a day so it wouldn't get worse, well it did and we let it sit for a month or so and today we started trying to find the problem and help fix it. We cranked it and the throttle jumped way up and dropped a little bit after my dad hit the gas. We took the fuel filter off and sucked the fuel out and put oil in and 2 stroke oil in the gas tank. After shaking the truck up a bit we cranked it, it went up in throttle but backed down and settled down like normal. After we let it sit for dinner idling it seems all normal except a little hiccup every 2 seconds in idle. Does anyone know what could be causing this problem exactly? We think its the fuel injector but I want more opinions before spending $600+ dollars.

Here is a video
https://youtu.be/EG5hAFeOfgk

Thanks, Phantomz

[svcattle]

do you have any codes ?

[Bravo51]

I really don't think it is an injector. It seems like it can't find idle. If you hold a higher rpm will it do the same thing? I would think it would be an injection pump related issue. I know there is a governor in there.

[DmaxMaverick]

It doesn't sound like an injector. A bad injector will typically be a fairly consistent miss. Air in the fuel (leak, failed lift pump, or LP circuit), failing PMD or IP, are much more likely suspects.

Because it's a 95, you can easily test the LP.....
E-brake (and/or chocks), key to ON (no start), gear to any position other than P or N, turn key to START. The LP should power and run, but the engine shouldn't crank. If the LP runs and provides sufficient pressure and flow (4-10 PSI) with the engine off, but doesn't with the engine running, suspect the OPS (Oil Pressure Switch) or the circuit. Slightly less common could be the ign. switch.

The governor is electronic (PCM controlled), so if the RPM's are wrong, it's the IP or fuel supply causing it.