95 Chevrolet k1500 5.7 tbi issue

Discussion in 'Engine Performance + Maintenance' started by Matthew Kesler, Sep 20, 2020.

  1. Matthew Kesler

    Matthew Kesler Newbie

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    Since everyone suggests fixing the tbi, I’ll see what I can get. So we just put new distributor cap and rotor, ignition coil, plugs and wires. New fuel pump and filter, new IAC valve, new throttle position sensor, and at one point new map sensor but the old and new didn’t make a difference. The truck when we got it had a terrible idling issue where it would hardly stay idling and wouldn’t hardly start at all and you had to wait before starting it and it’d kick over and you’d have to two foot it to drive it but it would drive fine with plenty of power. Now after we replaced all that stuff, it still surging in idle occasionally (only when warm) and bogs down hard when a/c and lights kick on and surges, then it will smooth out. Then after you get it to smooth out, it’ll stall completely when it goes in gear and then won’t start back up. You have to wait 10-15 minutes and try to crank it and it’ll hit once and the second time it’ll start if you give some gas and it’ll surge again and rinse and repeat. Happens every time you want to drive it. Then once you get it driving and going, it’s just like normal with no surging or two footing, or anything but problems start when the truck shuts off for a while and you wanna go somewhere else. Just about 30 minutes ago I got stuck at Wendy’s becaus truck wouldn’t even start up at all, cranked over multiple times and wouldn’t even kick. Then we took air breather off and tried it and it started right up and drive home. With air breather off, it seems to hesitate when you try to rev it up a little and will bog down a little if you quick rev it and let the rpms go down. At a loss here. Sorry for the huge paragraph.
     
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  2. MIHELA

    MIHELA 1-5-6-3-4-2-7-8

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    Is it getting proper fuel pressure?
     
  3. PlayingWithTBI

    PlayingWithTBI Desert Old Guy

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    ^^^X2 that's the 1st thing I'd check. GM says your pressure s/b 9 - 13PSI but the consensus here is closer to 11 - 14. 10PSI is marginal.

    Then I'd look at the distributor pick up coil, ICM and circuitry.

    https://easyautodiagnostics.com/gm/4.3L-5.0L-5.7L/distributor-mounted-icm-tests-3

    You're either not getting enough fuel or spark, just need to figure out which, or maybe both.
     
  4. Matthew Kesler

    Matthew Kesler Newbie

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    Well our mechanic said he replaced the fuel pump with one that gave 65+ psi, but not sure, i'll have to check it again.
     
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  5. MIHELA

    MIHELA 1-5-6-3-4-2-7-8

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    The regulator could have a broken spring or torn diaphragm, regardless of pump pressure. It should be 10-12 PSI. Without checking you are just blindly hurling parts at it.
     
  6. LC2NLS6

    LC2NLS6 I'm Awesome

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    It has air, it has spark. Betting fueling issue. You can rent a fuel pressure gauge for free at autozone. I stuck it down at the fuel filter since my truck had hard lines to the TBI that were bolted in place to the block. Then could be clogged or bad injector? If you are super careful, you can remove the TBI and injectors case. Then see if maybe the screens in the injectors are clean? Do not tighten them back down much, I have a snapped one as proof that metal is very brittle.
     
  7. Matthew Kesler

    Matthew Kesler Newbie

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    I am going to check fuel pressure, check for vacuum leaks and look at injectors to see if they are spraying good because I don't feel like tearing into a TBI right now lol
     
  8. LC2NLS6

    LC2NLS6 I'm Awesome

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    Even if it has correct fuel pressure, doesn't mean the injector screens aren't clogged up.
     

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