Hesitation off the line

[Corster]

Background: Just bought this truck (in signature) last weekend. Been driving it all week for work.

• Engine replaced at 65K
• Fuel pump just went out and was replaced by a shop
• Operates fine at speed

Question(s): Is it typical for the 5.7L to hesitate off the line trying to get up to speed? Could this be a weak fuel pump?

 

[Jay33089]

Could be a spider issue. Also remove your egr valve and see if it's got crud in it. You can unplug the egr and drive it to see if the hesitation goes away. Keep in mind the check engine light will come on. But doesn't effect the way it runs. Even if it looks clean try unplugging it. They get weak over time and when you start off the pressure from the exhaust will cause it to fly open momentarily causing it to lean out. Had this issue on my 98. As for the spider fuel pressure test should reveal if it is the culprit. In my experience when a pump is weak it runs terrible all the time. But strange things can happen!

 

[94burbk1500]

That's not the norm, I doubt it's the pump though. Jay has some good points. Disconnect the egr and see if it runs better. Mine was disconnected when I bought it, hooked it up and had similar issues to what you're seeing. Idk about the spider as mine is tbi, but I know they can be problematic as well.

 

[Corster]

Thanks fellas, will try that out and check back if I find anything.

It goes into the shop on Sunday for tires, alignment, oil change, and possibly fan clutch replacement. I might have them test the fuel pressure and inspect the EGR also.

 

[L31MaxExpress]

Thanks fellas, will try that out and check back if I find anything.

It goes into the shop on Sunday for tires, alignment, oil change, and possibly fan clutch replacement. I might have them test the fuel pressure and inspect the EGR also.

I suspect EGR as well. Back before I tuned the Express van to disvale the EGR I got the same little hesitation that got progressively worse. Using a scanner you could see the PCM command a 10% or 20% opening amd see a 50% response from the feedback circuit. The PCM took alot of miles to finally throw a code. Put a new GM valve on it and the problem disappeared. The internal spring had broken on mine that helps keep the valve closed.

 

[Corster]

Thanks for the info @L31MaxExpress. EGR I can do myself, so I will get the work done on Sunday at the shop and save a few $$ and do the EGR in the coming weeks.