95 s10 4.3TBI runs like crap under a load

Discussion in 'Other Auto Tech' started by Foxfan88, Oct 9, 2007.


  1. Foxfan88

    Foxfan88 My Grandpa has great wood.

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    ok my pickup has always ran bad under a load since i got it. wasnt too bad at all.
    it would pull it itself.

    well its been getting worse, the car will idle good on a cold start and now when i try to drive away in the morning it will fall on its face and run bad, buck and not pull it self. it will clear up, but still do it over a certain rpm.

    the problem only occurs past a certain rpm, if you keep it LOW rpms and lug it around it drives good. once it gets past a certain rpm the car acts like it doesnt have fuel or something.

    i checked plugs, they are good, replaced fuel filter.
    thought it was a clogged cat, took it off, still acted up. the cat had broken up so i thought it could have went back into the muffler and clogged it up. replaced the muffler

    the truck can drive well and when you part it, say you let it sit for 15 mins, it will fire up and idle fine. but if you wait say 45 mins where the engine starts cooling down. upon startup it will surge and try to die, you have to feather the gas ( pressing the gas will stall the engine, when your letting your foot off the pedal is when it revs up)

    also when its falling on its face. say i am giving it gas to accelerate, it will fall on its face and not pull at all, but as i let off the gas it will pick up and act fine, but only while i am lifting off the gas pedal which is less than a second lol

    i am guessing it may be the fuel pump, only think i can think of that would get worse and worse over a long period of time.

    any ideas?
  2. Darkwriter77

    Darkwriter77 Resident Ranting Negative Nancy

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    Sounds almost like it's running rich, actually, if it gags when you dip into the throttle - it's being force-fed its fuel at a pace faster than it can handle, for whatever reason.

    Random ideas: fuel pressure regulator, IAT sensor (causes all kinds of weirdness), or misc. vacuum leaks.

    When you pulled the plugs, did they look black and kinda wet? Or fouled out in any way by funky deposits?
  3. timeless2

    timeless2 Vi Veri Veni Versum Vicus Vici Admin Dude

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    My pop's 1988 GMC S-15 had many of these symptoms. The shop replaced both the fuel pressure regulator and the fuel pump at the same time. It resolved the issue.

    You might try the cheaper of the two in order to rule the other out. These are just some ideas of where to start. Good luck, and let us know how it goes. :)
  4. Foxfan88

    Foxfan88 My Grandpa has great wood.

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    i didnt pull them all but i pulled 2, i was in a hurry, they were white and had a slight red to them, not much.

    i will try the FPR and see what happens, it does feel like its loading up
  5. Shiroelex

    Shiroelex There's nothing worse than aut Founding Member

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    I've encountered this problem before. There's a plastic fuel line that runs through the upper intake, and it leaks all over the place in there. The one I replaced had tons of fuel puddled up in the intake. I just pulled off the top half of the intake, primed the fuel pump, and watched the fuel shower. It's a pretty common problem, from what I have discovered. Problem is, it's past all pressure test points, so everything will read right up until that point. It's the last tube that fuel goes through before going into the injector.

    Also, is your avatar Cid? It looks familiar.
  6. Foxfan88

    Foxfan88 My Grandpa has great wood.

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    yeah its cid
  7. Shiroelex

    Shiroelex There's nothing worse than aut Founding Member

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    :nice:
  8. vp6799

    vp6799 New Member

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    If it's the 4.3L Vortec motor, this might help you. There very well known for this problem and it will cause your symptoms.

    The problem is common with all the GM vehicles made between 1992 - 1995, that have the 4.3L Vortec vin code "W". The 4.3L Vortec has a CPI (Central Port Injection) system that has proven to be quite problematic. These injection systems consist of a large fuel injector that has tube going to each cylinder (six total). This injector is located in the plenum. (must remove upper intake to see it) The problem with these systems is that they develop leaks, these leaks occur in either the FPR (fuel pressure regulator) mounted on the side of the injector or the internal fuel lines leading to the injector assembly (GM has decided to refer to these internal fuel lines as a "Nut Kit" for some reason). The FPR is located on the passenger side half of the intake, and the nut kit is located on the driver side of the intake. The cylinders on the side that develops the leak, get flooded by fuel causing a rich condition. This rich condition can cause the engine to run rough, create a strong smell of raw fuel, set O2 sensor codes, cause excessive carbon build up that plugs the EGR valve, set EGR codes, and/or cause raw fuel to enter the oil which destroys the engine.
  9. Foxfan88

    Foxfan88 My Grandpa has great wood.

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    i got it fixed a week ago lol it was the fuel pump i forgot to post it
  10. Darkwriter77

    Darkwriter77 Resident Ranting Negative Nancy

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    The '89 S10 Blazer I just got with a 4.3 TBI is doing exactly the same thing as described above. Already scored a fuel pump. This thread gave me a good direction with which to go on it. :cheers:
  11. Darkwriter77

    Darkwriter77 Resident Ranting Negative Nancy

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    UPDATE: Replaced the fuel pump. No change. Replaced the fuel pressure regulator. Still no change. Going to test the ignition module next - if it turns out to be the culprit, I'm going to feel like a complete idiot for not having thought to check that first. :nonono:
  12. Darkwriter77

    Darkwriter77 Resident Ranting Negative Nancy

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    ANOTHER UPDATE: The ignition module was bad. Replaced it. STILL NO FRIGGIN' CHANGE. It won't start at all, now. Only thing left I can think of is the injectors, themselves, or for some reason the injectors are not being commanded to fire - bad connection, bad ECM, bad mojo, whatever. :shrug:

    I shoulda' kept the HARBL... :(

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