5.7 Vortec issue.

[rs74]

So I have been having an issue with my 2000 K2500 since I bought it. It doesn't want to rev or go without having hesitation and some bogging. When in park running and you floor it it hesitates really bad, has a bogging sound and sometimes coughs but after a few seconds it eventually revs up. While driving it the truck is really sluggish when on the throttle like it has no power. I just did a tune up and fuel filter minus coil. Checked fuel pressure today and we have 57-8 KOEO, 52-3 running at idle and spikes to 60-62 when hitting the throttle. Seems like pressure is on the low side but is it enough to cause this issue?

The only other things that comes to mind is either the spyder injectors or maybe plugged cat. I need to see if I can see on my scanner what the timing is while running too. At a loss at this point in time.

[speedygonzales]

Spec is 60-66PSI KOEO. See how fast pressure drops off. Could be an injector stuck partially open.

Check plugs to see if one is running rich. If so you should check the dipstick for the presence of gas in the oil.

Obviously to check the cat, disconnect it and see how it behaves.

Have it scanned for the presence of history codes and check the ECT sensor to be sure its reading the correct temperature.

[rs74]

Originally Posted by speedygonzales

Spec is 60-66PSI KOEO. See how fast pressure drops off. Could be an injector stuck partially open.

Check plugs to see if one is running rich. If so you should check the dipstick for the presence of gas in the oil.

Obviously to check the cat, disconnect it and see how it behaves.

Have it scanned for the presence of history codes and check the ECT sensor to be sure its reading the correct temperature.

The only code that showed on my scanner was a P0463. Fuel sender input signal high.I will have to follow up on the rest.

[Tom]

Yes, your pressure specs are enough to cause this. Same kinda low pressure situation caused my truck to cough at anything over 50% throttle, ran fine otherwise. Weird stuff these fuel injected motors lol.

[rs74]

Originally Posted by Tom

Yes, your pressure specs are enough to cause this. Same kinda low pressure situation caused my truck to cough at anything over 50% throttle, ran fine otherwise. Weird stuff these fuel injected motors lol.

I will probably order a new fuel sending unit and regulator. I took it out today and it was running fine then when I took off from a stop sign it just started popping and coughing real bad for a few seconds then came out of it.

[speedygonzales]

I wouldn't just replace things. A bad fuel pressure regulator could be the issue. Certainly a bad poppet valve would not be cured by another pump. You could invest in a fuel pressure gauge that has a hose long enough to tape the gauge to the windshield and drive around and see what the pressure is doing when the problem occurs.

Throwing money at the problem rarely cures it.

[rs74]

Just figured a new pump was in need if it is already under spec. There should be enough hose on my fuel pressure gauge where I can take it down the road and see what it is doing. I will give that a try.

I can say this. When I initially hooked the gauge up and revved it in park, the pressure spiked to a steady 62 psi while the engine was struggling to rev up as it should.

[rs74]

Today's readings are different. KOEO was 46 psi and bled down to 43 in about ten seconds. Start up at idle was 43 spiking to 46 when giving gas. Running for ten minutes now at 45 psi and little fluctuation when giving it gas.

The engine will Rev smooth to about 3500-4000 if revving somewhat slower and steady. If flooring it then it wants to stumble as it climbs it's rpms. Truck is still idling smooth.

[rs74]

Disregard that whole last post. I think the tester I bought is junk. Going to see if I can buy another and take this one I just bought back.

[rs74]

Okay. Bought a new fuel pressure tester today. 52 KOEO, 52 running at idle and spikes to 61. Bleed off was very minimal if any from what I saw. Still quite a bit under spec.

[speedygonzales]

Your numbers the first time made more sense and really weren't that far off. These numbers make NO sense at all. It's nearly impossible to have the same number idling as before running.

Did you ever even pull one plug? Much less one bank?

I'd go for a FPR first. Not hard by any means but time consuming. Get an upper plenum kit before you start and the new FPR of course. You will not like what you see under the plenum if you still have EGR, so prepare for the worst.