engine trouble 305 Vortec

[z71Tom]

I am having trouble with my work truck. Its not a gmt400 but a close relative. 2001 Chevy Express 2500 305 Vortec. Its got 242,000kms on it.

These are the symptoms:

It boggs when throttle is applied any more than just enough to get you going.
If your real easy on it it gets around but from a stop or any speed, any time you apply some throttle it boggs drastically and backfires through the intake, until you let off.

- The problem came on slowly and is getting worse.
- It randomly goes away completely for a day. You can hit it and has no problem reving up. Then you let it sit for a bit and next time you start it up it runs bad.
- No check engine light

So far I have changed fuel filter
checked the cat. (Apparantly its fine, but it's not written in stone.)
Tested fuel pressure. (Runs 50 psi to 54 psi) It maintains preasure when its bogging.
I am in the process of check exhaust back pressure

Any tips or Ideas would be appreciated. This truck is my livelyhood.

Thanks

Tom

 

[Aloicious]

I would venture a bet that its fuel related. your pressure is pretty low for a L30 vortec. typically they require 58-60psi for startup, and ~55psi while running, this is because the injectors use pressure to open. even a few psi too low can cause it to not even run. there are a few things that could be happening, either you have a fuel pump that is starting to go, or its possible that you have an injector/regulator/metering body leak somewhere that is bleeding off a little bit of pressure and making a few cylinders run rich. both of those scenarios could account for the symptoms, but either way at 50-54psi your pressure is too low, if it gets much lower the van may not run at all.

 

[DRAGGIN95]

Yeah it sure does sound fuel related, also I would suggest when you get it back running you run a can of seafoam through it, it would also be worth your time to use a live data code scanner and check out the TPS snesor, and various other sensor's in the data stream. Good luck and I hope it's an easy fix.

 

[Aloicious]

Yeah it sure does sound fuel related, also I would suggest when you get it back running you run a can of seafoam through it, it would also be worth your time to use a live data code scanner and check out the TPS snesor, and various other sensor's in the data stream. Good luck and I hope it's an easy fix.

yeah, if you have a live data scanner, try checking out what your O2 trims are as well, that will help you narrow it down too.

 

[rkadair]

I had this same problem on my 98 K1500 and it was the spider

 

[Blind]

my old truck did similar **** and it was the cat converter had plugged up the exhaust, it happened twice in 2 years. Started out as an exhaust rattle each time, then one day the exhaust just got completely silent and anything over a light touch of gas made it misfire and not be able to accelerate at all.

 

[z71Tom]

Thanks guys,
- So I think I'll confirm if its back pressure
- After that, fuel pump
.....

 

[Aloicious]

check fuel pressure with both key on engine off, as well as idling, and short driving.