2000 Chevrolet Silverado 4.3 vortec plague

Tiny
JONXSMITH
  • MEMBER
  • 2000 CHEVROLET SILVERADO
  • 120,000 MILES
I bought this truck at 89k miles, and in 2 years at 120k miles the problem still persists if not getting worse.
This truck is a Silverado 4x4 5spd with a 4.3 vortec motor.
Since I bought the truck its always had a problem at part acceleration, it always bucks, jumps and loses power, sometimes terribly, sometimes barely noticeable. I've changed the plugs, wires, and dist cap and button several times, changed the fuel filter, cleaned the egr, the maf, changed fuel filter, changed throttle bodies, and nothing to any avail. Recently It's been getting a little bit worse, it's always had a slight miss at idle, but you can kind of feel it now, and when going WOT, in 1st and 2nd it's fine, you can feel it lose and gain power throughout the rpm range, but it does fine. My gears are short due to 3.73s from factor, but when I hold out 3rd at about 4k rpms or so, it dies, and won't go past a certain rpm, when I change out of 3rd to 4th or 5th it misses like crazy, and won't accelerate, actually decelerates, it clears up after a while, but when I let off throttle completely it goes to <200k rpms and will almost shut off. I don't have the courage to see if it actually will.
Any help on this matter would be appreciated as it is driving me crazy, and I don't have money to be replacing a hundred sensors and parts like everyone online says to do.
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Sunday, July 21st, 2013 AT 12:16 PM

9 Replies

Tiny
DOCFIXIT
  • EXPERT
Is fuel pressure at 60-66 psi?
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Sunday, July 21st, 2013 AT 12:37 PM
Tiny
JONXSMITH1
  • MEMBER
This is the OP, I messed up the email address when I created my account, I haven't checked it yet, I'll go check it and see what I find out and get back to you when I have the numbers. Thanks.
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Sunday, July 21st, 2013 AT 12:57 PM
Tiny
DOCFIXIT
  • EXPERT
O.K. Be on line till about 4pm EST then back on Monday
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Sunday, July 21st, 2013 AT 1:07 PM
Tiny
DOCFIXIT
  • EXPERT
Sorry 5pm
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Sunday, July 21st, 2013 AT 1:07 PM
Tiny
JONXSMITH1
  • MEMBER
Ok, got a fuel pressure tester, I've never done this before, so I may not have gotten all info needed, but anyway.

At idle, needle jumps rapidly between 53-55psi, at half throttle evens out around 50psi, and when going full throttle and revving it will jump to 60 and drop back down to around 50
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Sunday, July 21st, 2013 AT 2:10 PM
Tiny
DOCFIXIT
  • EXPERT
You have found problem needle should be steady and not fluxuate. Seen this hundreds times usually with code P0300
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Sunday, July 21st, 2013 AT 2:26 PM
Tiny
JONXSMITH1
  • MEMBER
Well, I have never performed a pressure test, but one of my buddies said when he tested his on a different vehicle you had to pull a vacuum line off fpr but I didn't know how to with the fpr being under the plenum.
If none of that mattered in the test, is it more likely the pump, injectors or fpr?

Thanks for your time
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Sunday, July 21st, 2013 AT 3:24 PM
Tiny
DOCFIXIT
  • EXPERT
Vacuum line off pressure relief will let pump max pressure pump must maintain 60 -66 with PRV hooked up and never flux think about the problem does it not seem like low fuel delivery my 48 yrs in business says yes
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Sunday, July 21st, 2013 AT 4:03 PM
Tiny
JONXSMITH1
  • MEMBER
Alright, I'm gonna see if I can straighten it out, thank ya for your help
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Monday, July 22nd, 2013 AT 12:52 PM

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