Rough Idle and shaking at acceleration help!!?

[jrfinchen1]

Hey yall, I have a 1992 chevy k1500 5.7 350 all stock and im having an issue with rough idle and poor acceleration when I drive. My fuel pump went out recently and I replaced it and the filter but I still had a rough idle seemed like it wasn’t getting enough fuel. When I would drive it seemed to drive fine, now all of a sudden today it started to have a shake at idle and didn’t want to accelerate without shaking so I went ahead and rebuilt my tbi, new injectors, egr valve and I am still having the same issue. Could i have gotten a lemon of a fuel pump? What other reasons could be causing this any information would help. Thanks.

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[Alteca]

Have you replaced spark plugs, wires, distributer cap and rotor? If u are sure it’s a fuel problem it could potentially be a poor connection issue. check grounds, power cables, etc…

 

[jrfinchen1]

Yes I replaced. Cap, rotor, spark plugs and wires this morning and still having issue. I checked the ground from the fuel tank so I'm not sure what it could be.

 

[Sabinoerc]

its not unheard of to have a bad fuel pump out of the box.

Either way, for problems like this you really need to check fuel pressure. Check between filter and TBI. Easiest is just after fuel filter as you can release fuel line up to TBI there and get some space. fittings to chec k pressure aren’t expensive. I bought one from Actron. I’ve heard they may have something at HF or loaners at parts houses but don’t know myself. Some put a pressure gage or test port at TBI to make it easier to check. I’d probably do that next time I have to get in there to work on something.

They say spec is 9-13psi. But I had new pump from Autozone running at 10psi and on my 93 5.7l old engine at least that was not good enough. It was also dipping when blipping the throttle. Replaced with Delphi and got a solid 13psi with no variation and my similar problems went away.

Many things can cause your problems but first thing to check is that you have good fuel pressure.

 

[PlayingWithTBI]

They say spec is 9-13psi. But I had new pump from Autozone running at 10psi and on my 93 5.7l old engine at least that was not good enough. It was also dipping when blipping the throttle. Replaced with Delphi and got a solid 13psi with no variation and my similar problems went away.

Yep, I'd prefer 11-13, even as high as 14PSI for a stock TBI.

 

[jrfinchen1]

its not unheard of to have a bad fuel pump out of the box.

Either way, for problems like this you really need to check fuel pressure. Check between filter and TBI. Easiest is just after fuel filter as you can release fuel line up to TBI there and get some space. fittings to chec k pressure aren’t expensive. I bought one from Actron. I’ve heard they may have something at HF or loaners at parts houses but don’t know myself. Some put a pressure gage or test port at TBI to make it easier to check. I’d probably do that next time I have to get in there to work on something.

They say spec is 9-13psi. But I had new pump from Autozone running at 10psi and on my 93 5.7l old engine at least that was not good enough. It was also dipping when blipping the throttle. Replaced with Delphi and got a solid 13psi with no variation and my similar problems went away.

Many things can cause your problems but first thing to check is that you have good fuel pressure.

OK, thank you for your feedback. I'm going to go ahead and check fuel pressure.

 

[jrfinchen1]

its not unheard of to have a bad fuel pump out of the box.

Either way, for problems like this you really need to check fuel pressure. Check between filter and TBI. Easiest is just after fuel filter as you can release fuel line up to TBI there and get some space. fittings to chec k pressure aren’t expensive. I bought one from Actron. I’ve heard they may have something at HF or loaners at parts houses but don’t know myself. Some put a pressure gage or test port at TBI to make it easier to check. I’d probably do that next time I have to get in there to work on something.

They say spec is 9-13psi. But I had new pump from Autozone running at 10psi and on my 93 5.7l old engine at least that was not good enough. It was also dipping when blipping the throttle. Replaced with Delphi and got a solid 13psi with no variation and my similar problems went away.

Many things can cause your problems but first thing to check is that you have good fuel pressure.

Did you replace just the pump or the entire unit and pump?

 

[Sabinoerc]

Did you replace just the pump or the entire unit and pump?

I just replaced the pump and fuel filter. Fuel filter has a direction arrow, make sure you put it in the right direction.

 

[Schurkey]

As usual, you'll need to verify fuel pressure, and connect a scan tool to verify all the sensor inputs to the computer, and the computer outputs to the injectors, EGR, IAC, timing advance, etc.

If you're going through the trouble of lifting the bed or dropping the tank to put in a fuel pump:
1. Don't forget to replace the strainer sock at the bottom of the pump

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2. Replace the in-tank wire harness. They corrode especially with water/alcohol in the fuel.

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3. The rubber hose between pump and the "hanger" tube is "special"; not all fuel hose is rated for SUBMERGED use. And use decent clamps, not the crappy non-shielded, worm-gear junk.

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Other applications use a pulse-dampener instead of a plain rubber hose. If the damper diaphragm is ruptured, you'll lose fuel volume and pressure.

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