Truck stalling randomly with load (at stop light, turning wheel to maneuver at idle speed)

Discussion in 'The Engine Bay' started by RockBottomRacing, Nov 12, 2020.

  1. RockBottomRacing

    RockBottomRacing Registered Member Premium Member

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    1991 TBI 350 in my V2500 Suburban. She’s acting like the IAC is slow, like instead of the idle picking up to compensate for the vacuum pull for the brakes at a stop light or the power steering load in tight turns, it idles low and chokes out. When I unplug the PCV valve line from the front of the throttle body the problem almost goes away. New OEM PCV valve. New IAC from Napa. Also, if I plug the PCV port on the front of the throttle body, the truck dies instantly. Cold or hot. My old K5 had the PCV port capped and it ran like a banshee.

    When I changed the IAC I pulled the throttle body and cleaned the shit out of the passage ways. New gasket for the throttle body base and the air cleaner base. I’ve tested other vacuum lines and no change. I haven’t messed with the TPS, I did check voltage and it was normal, I haven’t done map sensor, or egr controller. I replaced the vacuum lines for my cruise control and cruise control works perfect. Truck has the 4L80e. Only code I get is for EGR at highway speeds. Engine doesn’t have blow by. Starting to get pissed at this thing, so if someone has some ideas here, it would be greatly appreciated!
     
  2. RockBottomRacing

    RockBottomRacing Registered Member Premium Member

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    Anyone? Stalled on me again today -.-;;
     
  3. diesel4me

    diesel4me 1 ton status Premium Member

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    EGR valve might be hanging up open ?...that'll let exhaust gases back into the intake,same deal as a vacuum leak but with exhaust gases instead of clean air...
     
  4. ktmoutfront

    ktmoutfront GnomeWorks LLC Premium Member GMOTM Winner

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    What you are describing with plugging the PVC port and it quitting, it is not receiving enough air through the butterflies. Closing too far and sealing. I do not remember what those TBI's look like. Is there a throttle stop that can be adjusted? What is the engine RPM at idle out if gear and in gear?
     
  5. Wes Harden

    Wes Harden 1/2 ton status Premium Member

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    What is the idle speed does it seem slow or normal?
     

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