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  1. #1

    Unhappy 91" Chevy Truck W/350 Weird Problem??

    Greetings all and thanks for reading.
    I have a problem with my 91 silverado 350 pickup. When i start it up it runs fine until I stop and shut it off for a short period of time. Then when I restart her she starts running rough. If I feather the gas pedal I can keep it running but boy its rough. After a few minutes (and sometimes it won't) it will start running fine again. Checked and cleaned EGR, cleaned IAC, new coolant temperature sensor.

    Its weird because it will run fine until I shut it off for maybe 10-30 minutes then try and restart. Then the rough running engine starts to happen. Yesterday after leaving home depot which was 25 miles away from where i live. Came out started it, as usual ran very rough, but i feathered the pedal to the freeway and got her up to speed and when I got off she was running fine (like a champ).

    Hope someone can help with this mystery. It has 112000 miles on her.

    Thanks for your time.


  2. #2
    Jr. Mechanic
    Join Date
    Apr 2013
    East Central Iowa


    Check for a vacuum leak. may not be very big. Other possibility the coil may be starting to go.

  3. #3


    Thanks for the response zzipstripp. Like your handle! Sounds like you like to catch flys (lol).
    Anyways I check for leaks in vacuum lines and could find none. Took coil to Auto Zone and they said resistance was in specs. Could you think of anything else?

    Thank again
    (need oil)

  4. #4
    Sr. Apprentice MAD JAX's Avatar
    Join Date
    Aug 2013
    At Large ; )


    IF it smokes like H.E. double Hocky Stix (HELL ; ) immediatly after "Hot-Restart" then Your valve-guide seals are baked to a delicate crunch ~ Engine Oil is dripping through, onto the Valve "Tulip" to "Puddle", and otherwise directly into the Cylinder from the Valve-Stem, off the open-valve "Tulip" and onto the Piston ~ thereby fouling the Spark Plug until it runs long enough to "Clear" itself : ?

    Otherwise/Including-too: You may have leaky Injector(s) causing the problem in somewhat the same-way for having fouled the Spark Plugs : ?

    Otherwise too: Either Fuel System "Vapor Lock" due to Line Pressure Drop OR Ignition System break-down ~ BOTH due excessive "Hot-Soak" (Under Hood) temps...unless it's NOT "Summer" wherever You are of-late : ?

    Good Luck, Be Safe ~ WEAR SAFETY GLASSES and HAVE A FIRE EXTINGUISHER HANDY AT ALL TIMES! (You never know when you'll want to hose SOMETHING down with it... ; ) Ciao, M.J.
    "Impossible" is a degree of difficulty ~ set by imagination for lack of motivation.

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