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fresh motor and new tbi and truck bogs down

Discussion in 'Chevy Trucks' started by BIGRED1, Dec 3, 2005.

  1. BIGRED1

    BIGRED1 Member
    Messages: 44

    Ok here it is, 1990 chevy 1500 4.3 6cyl. @ 206,000 motor ceased (R.I.P.) replced with a GM replacement engine ($2100 installed). Good deal, I was happy, truck ran great. Then the throttle body went bad and my guy replaced it and it ran great again, but very very quickly I noticed that when I put my foot into it it would die or bog down. I would have to back out of it and try again slowly and she would pick up slow. My guy says its a fuel filter problem but I can't help but wonder if the throttle body is out of whack or needs adj.

    also, when I drop it into low 1 it seems to help and BTW my mechanic (former mechanic) is lazy and doesn't wanna work on it anymore

    anyone have any ideas. I have too much $ into this truck for it not to run excellent

  2. Sounds like the fuel pump to me, Did the same thing on my Iroc-z back in the day:). That's the way it started happening and then it just progressively got worse.
  3. BIGRED1

    BIGRED1 Member
    Messages: 44

    dumb question but...

    Is the fuel pump a big deal on this truck, damn it just hit me, its in the tank isn't it... Son of a .. I'm gonna have to drop the tank aren't I
  4. derekbroerse

    derekbroerse 2000 Club Member
    Messages: 2,377

    Yes it is. PITA but not really THAT bad...

    Soak the bolts with oil a few days ahead of time.
  5. Jim Prill

    Jim Prill Member
    from Zion Il
    Messages: 74

    Make shure the wires going to the injectors arnt broken or pinched at the grommet where the air cleaner mounts I have seen them get pinched there a few times. also check the knock sensor if its bad it will pull out all the ignition advance.
  6. icebladez

    icebladez Member
    from sask
    Messages: 74

    a off shot but a similar thing happened on a Daytona i once owned..could your plugs (spark) be all gummed?
  7. NJBuickRacer

    NJBuickRacer Member
    Messages: 59

    Connect a FP gauge with a hose long enough to see from the driver's seat. Watch fuel pressure when it bogs, if it's dropping out the pump is bad or the filter is very clogged. Since the problem started after the throttle body was replaced, it's possible the fuel pressure regulator in the replacement is faulty or the injectors are sized improperly for your application. Another possibility is a faulty throttle position sensor, or the sensor is not attached correctly to the throttle body. Using a voltmeter with the key on engine off, probe the TPS output. It should be .45-.80 at idle/closed throttle and around 4 volts at wide open throttle. The sweep should be smooth, any jumps to 4V or 0V at part throttle in the middle of the range are indicative the sensor is faulty.