1988 GMC rough idle, no power, stalls

Discussion in 'Engine Performance + Maintenance' started by gareth12, Jan 22, 2018.

  1. DerekTheGreat

    DerekTheGreat I'm Awesome

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    Well, that's certainly one of the sensors that are notorious for going bonkers. The engine will run with it unplugged, just not as good since it uses that information to determine how much fuel to feed it. Let us know how she does with a new sensor. More pics of truck needed, looks to be a real nice four eye.
     
  2. gareth12

    gareth12 Newbie

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    I put in the new ignition module, no better. Since i just LS swap stuff for a living i think i have forgotten how to be a mechanic lol. Anyway i rigged up another fuel pump and made up some fittings to get a gauge on it. Ran strong with another fuel pump, and had 6psi fuel pressure with the factory one. So i replaced fuel pump and filter and now it runs well.

    It still stalls however, it wont do it when its cold, only when its upto temp and idling. Revs seem to drop off a bit and it promptly dies after 6-10 seconds, does it like clockwork. I figured i would clean the IAC and when i pulled it out it popped apart. So i replaced that but it made no difference. Meanwhile i keep eyeing off the LS3 lol, and i think i will do a rack conversion, its been RHD converted and its a sloppy job.

    Any thoughts on the idle? Hard without a scan tool that will talk to it
     
  3. gareth12

    gareth12 Newbie

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    I have noticed driving it then that with clutch depressed and rolling the revs jump up a bit, or in nuetral and rolling much the same, its only when i come to a complete halt that it stalls out after 6-10 seconds.
     
  4. mountie

    mountie OBS Enthusiast

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    Throttle Position sensor bad?
     
  5. gareth12

    gareth12 Newbie

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    I will check that, i was suss on o2 sensor, or maybe even a vacuum leak
     
  6. Dan12valve

    Dan12valve Newbie

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    Is fuel pooling up on the back of the throttle blades while this is happening?
     
  7. gareth12

    gareth12 Newbie

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    Doesn't appear so
     
  8. Dan12valve

    Dan12valve Newbie

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    Disconnect a sensor like the tps or map. May be upset for a moment. It will stop reading the chip in the computer and kick over to the limp chip. See if it stays running.

    Can also unplug the egr solenoid, if you haven't already. Egr spring gets weak and will cause issues or it can leak.
     

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