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neverending TBI problems

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by Jonny-K5, Dec 20, 2005.

  1. Jonny-K5

    Jonny-K5 1/2 ton status

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    so heres the story. about three months ago my truck was running fine. i had a holley tbi. decided i might get better performance/fuel ecomony if i put the stock TBI on with upgrades( adj.fuel pressure regulator,injector spacer,TBI spacer). installed all the parts and the truck ran terrible. passenger side injector would not fire. replaced bad injector with new one from autozone. it now ran ok, but had a poor idle on cold startup and seems to miss/starve of fuel above 3000rpm&heavy throttle. i could also not get my fuel pressure to stay consistant. it would be 14 when i start it up, then go down to 11 after driving.

    so i decided to put the holley back on and hopefully fix all these problems. the full throttle miss went away, kept a steady 12psi,but still had crappy cold startup. drove it like this for a couple weeks, then i started to get a miss under cruise. almost like a hiccup. two days later it was so bad i couldnt even drive it.decided i had enough of this and towed it to my mechanic. we pulled the air cleaner and the pass side injector was not firing.for some reason my truck keeps killing that injector. he said since its happened on the other tbi,and there is no check engine light, its probly a faulty ecm. he replaced the ecm/prom with a "rebuilt" one, along with a dist. module.

    drove home and the truck ran fine. next morning still had the crappy idle @ cold startup, but ran fine otherwise. next day i started to get that hiccup. now today the hiccup is getting worse, and the idle isnt steady anymore again. im willing to bet the pass. side injector is starting to crap out again.

    any ideas? this damn thing is driving me nuts.
     
  2. BadDog

    BadDog SOL Staff Member Super Moderator Author

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    First off, verify that it is the same thing again. If it is, check the wires and plug on that side. There is nothing I'm aware of that would kill injectors on one side like that, my guess is it's not getting a signal.

    Fuel pressure drop after running like that is most likely the fuel pump. Changing TBs should not have affected that behavior. I recently saw similar things on my K5. Turned out to be 2 things. 1 was fuel pump falling off. The other was heat on the new underhood gauge. Turns out, when the gauge gets hotter, it reads lower.

    Bad behavior cold could be lots of things. Is the engine modified? If so, the stock ECM may not be able to keep it happy in open loop.
     
  3. mouse

    mouse 1/2 ton status

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    I would carefully check the wiring to the failing injector. Sounds like a problem very near the throttle body.
     
  4. zcarczar

    zcarczar 1/2 ton status

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    If your engine is stock get rid of that holley TBI, go back to a stock unit with a stock FBR and no TB spacer. Check your fuel filter and fuel delivery system to make sure you dont have any flow issues. Also check your wiring for shorts and broken wires.
     

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