1999 5 spd 7.4 dies at idle

Discussion in 'The Garage' started by Across281, Nov 6, 2019.

  1. Across281

    Across281 Newbie

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    I have been chasing this problem for about a year truck dies in neutral only at stop light after idling for 20-30s. I have replaced egr, cap/rotor, coil & wire. I do not believe it has any bad fuses. I do believe neutral switch on trans is out as my reverse lights do not come on (new bulbs). O2 sensor out? I'm stumped. It does not die when driving/rolling in gear or out.
     
  2. df2x4

    df2x4 Domestics only.

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    Have you checked for vacuum leaks?
     
  3. Across281

    Across281 Newbie

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    Yes-no luck tracking one down. Sprayed starter fluid around intake manifold as well to make sure that was sealed.

    forgot to mention also replaced injectors and fuel pressure regulator-small hose to fpr was hard so did not replace
     
  4. Mangonesailor

    Mangonesailor I'm Awesome

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    You have to unplug the IAC valve to test for.leaks with starter fluid or otherwise. Otherwise the o2s will see the AFR change and pull fuel.

    Does it skip or anything or just suddenly shut off? Vapor lock maybe or fuel injectors?
     
  5. Across281

    Across281 Newbie

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    Ah ok i did not unplug IAC, sometimes it idle will drop to say 600 and bump back up. other times at idle it just shuts off. I do not suspect injectors because trying to track down the problem replaced fuel pressure regulator and figured while I was in there replace stock with bosch 4 hole injectors.
     
  6. Ron88

    Ron88 Newbie

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    Disconnect EGR plug line RE try?
     
  7. Across281

    Across281 Newbie

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    I replaced IAC today, it runs much smoother but still died on me at idle once warmed up still

    , looking into tps??

    Ronn88 I will try disconnecting egr, I actually replaced it a few thousand miles ago but have not tried to run with it unplugged.
     
  8. Philhammerjr

    Philhammerjr Newbie

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    I had a tps cause some idle issues on an s10 for about a year before finally setting a dtc. It would usually idle way higher than normal but never died. It would only have issues once the engine was warm. I assume no codes? Any correlation between engine temp and the dying?
     
  9. Across281

    Across281 Newbie

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    Phil no codes, and yes if engine is cold no problems.

    I can let it idle in my driveway for ever if I havent driven it. May just be fine in my driveway, only seems to die if I am at a stoplight or somewhere I dont want it to die. No hesitation just falls flat on its face, no problem restarting.
     
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  10. Mangonesailor

    Mangonesailor I'm Awesome

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    Man, maybe doing a datalog would be your best bet to figure this one out. But, TPS could be likely. You could backprobe and see if the resistance change is linear going to the shut position... or at least consistent.
     

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