94 chevy silverado k1500 4wd 5.7

Discussion in 'General Chevy & GM Tech Questions' started by therik, Mar 25, 2013.

  1. therik

    therik New Member

    hello I got a 94 chevy Silverado, my issue is when its wet and moist out like from all this snow we getting here in the Midwest, my truck will start up and start to warm up just fine after running for about 5 to 10 minutes. After such time it will rev up and down while idling until finally it just dies. But when im driving it if I hold the pedal steady the motor will just slowly die out unless I pull my foot from the pedal and reapply it it will rev back up a short time and it will just keep doing it until i turn it off, i replaced rotor, cap, wires, plugs, and ignition module. i looked over the distributor cap and it has no cracks. im wondering if it might be the coil or maybe the voltage regulator in the alternator. i do notice when it its acting up it basically dumps gas in, cause the gas gauge will steadily just flow down just trying to drive around town. any opinions or informed guesses appreciated. thank you
  2. geo1

    geo1 Member 100 Posts

    how did the plugs look?running rich or lean?try unplugging vac.hose from map sensor and plugging source,test drive
  3. Skippy

    Skippy Member 2 Years 100 Posts

    Wow, with those conditions, it could be any number of things. My first thought was a bad Air Intake Control Valve (IACV), because of the surging while idle, but thinking about the whole of the problem I realized the IACV wouldn't be doing much harm if you had your foot on the gas (the open throttle will negate any IACV problem).

    Then I got to thinking this could be an intake manifold gasket leak, which could create these conditions. Spray some starting fluid around the intake manifold while it's having problems (careful, this stuff is flammable!) and see if you can find a leak. If it's not that, I suspect a bad fuel pump. Low pressure could be causing the engine to compensate with throttle response, which is what you're doing with your foot. Connect a tester to the line and ensure it's got the pressure required (that could be tough while driving).

    That's my thoughts anyway... I'm leaning toward an intake leak given the gas dumping... usually it's not a problem of "too much gas consumed" if the pump is bad.

    That's where I'd start! Good luck.


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