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  1. #1

    Question 89 k1500 TBI idle problems

    Ok im new so if anybody could help me out id appreciate it..

    i just droped a remand jasper 350 in my
    truck and now the thing dosnt want to idle. some days it runs pretty good some days it runs like crap. i toped the new motor off with a brand new edelbrock preformer man, new distributer, plugs,wires,waterpump,iac valve an entire new fuel sending unit, fuel filter pretty much everything but the TBI its self is new under the hood... i warm it up in the morning, some days the idle is smooth as glass, some days the idle surges up and down to the point where it almost dies. i pull up to a stop light it does the same thing.. i have to keep a little bit of foot in the throttle to keep the idle up 95% of the time. ive shot the entire manifold with starter fluid to find and leaks, nothin, i cant hear the injectors surging, i cant find any vacume leaks and im about to go crazy. i dont know if its the map or what? anbody have any ideas?


  2. #2


    The best thing you could do is take it to a shop and have it diagnosed. It could be a bad ground somewhere, faulty o2s or maybe a vacuum leak.
    '00 1500 4x4 4.8l
    single glasspack
    daily driver/workhorse

  3. #3
    Sr. Engineer ahm1127's Avatar
    Join Date
    Jan 2009
    Pennsylvania, United States


    Sounds like vacuum leak or ground as nos351wcm stated. Check your vacuum lines and base of TBI , also remove & retighten all ground wires with dialectric greese before you bring to shop.
    Everyday I wake up is a great day! ;-)
    05' Chevy Suburban, 11' Ford Fiesta

  4. #4

    Default egr

    take and unplug the vacuum hose to the egr and plug it with a nail or something and drive it for a couple days the check engine light will come on after a bit but that is a common problem that will cause different idle problems

  5. #5


    so many of these trucks are having similar problems, but everyone seems to have a different cause for it.

    personally on mine, the diaphragm pod on the back part of the TB was leaking gas, causing the computer to over-correct for it, by adding too much gas, then immediately cutting gas off due to there being too much being thrown in.

  6. #6


    Is not the diaphragm pod on the throttle body actually the fuel pressure regulator or are we talking about something else.
    I would agree that is the most likely cantidate considering everything you've replaced. Luckily its a fairly cheap kit (you need the kit for gaskets and seals) from the auto parts store. Just try to keep old gasket crap from falling down into things. O and bleed off fuel pressure first unless you want to wear it.
    Last edited by 92WT; 02-04-2010 at 08:12 PM.

  7. #7


    I replaced my tps and erg valve and a set of hot ac deco rapidfires cause mine did the same now it's smooth. mine was doing the samething mines an 89 350.maybe test your coil or ign module.I put all performance ign parts on my 5.7.Just a thought.
    Last edited by 89classic; 12-25-2010 at 09:21 PM. Reason: to add more info

  8. #8
    stephan's Avatar
    Join Date
    Sep 2010
    Far West, Oregon USA,
    Blog Entries


    That's good advice 89 Classic, & welcome to the GM truck club
    1988 Chevy C-3500 2wd (no pic)
    350 c.i. 5.7 L Stock Block, 4 Bolt Mains
    L-31 Vortec Heads, Edelbrock Cam & Intake,
    Holley 650, Flowtech Headers, Magnaflow exh.
    Jet Trans 700R4, B&M Ratchet, 4:10 gears,
    3" susp. lift kit "shadetree"
    No rev limiter, No speed limiter lol

  9. #9


    WELCOME, i cant read that small sorry ...

    1996 Suburban K3500 SLT DUALLY
    1988 Camaro RS 383 stroker LT1
    1992 32' Aero-tek Race Boat, 600 CI BBC

  10. #10


    could be egr, or could be O2 sensor. O2's don't get read, and egr isn't kicked in, until the truck starts warming up, so either of those could easily be the culprit. Is it throwing any codes?
    1986 Chevy G20 Tow Rig - 5.7 TBI conversion
    1978 Mustang II King Cobra Road Racer - Holley 650, MSD 6AL, 5 speed, 10 point Roll Cage, 9" posi, fuel cell, custom interior.

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