Chevy 1/2 ton 2wd 4.3 vortec rough idle tried everything I know
Checked all sensors and changed out fuel pump (wouldn't start otherwise). Engine surges but drives ok @ driving speeds (except tranny won't shift into 3rd gear). The only thing I haven't tried is draining out the old gas - it smells terrible and refilling.
Re: Chevy 1/2 ton 2wd 4.3 vortec rough idle tried...
I had the same problem with my 96 Chevy 4.3. It idled rough enough to shake the truck at a stop. It revved up fine but sputtered on take off. My truck did not want to stay in overdrive because of the low rev. I changed cap, rotor, plugs, wires and this did nothing. Finally I took the intake off and found corrosion on the side intake gaskets near the rear of the engine causing a vacuum leak.
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two things pop to mind with this truck, first these motors are notorious for having bad intake gaskets take a flashlight and look very carefully around the valley of your intake/block-head seal you'll possibly see either antifreeze leaking or a weird looking whitish or greenish sort of foam you can also use propane around the seal and look for obvious idle changes, I have done tons of these intakes in my shop, the other two things I would suspect if that looks fine are 02 sensors, or maf sensor.
Here is some ideas coil pack, out of time, new wires, dist.cap, throttle position sensor, idle control valve, or take you air hose from air filter and check the wire screen inside you mass air flow sensor and make sure it's not plugged. That year of truck can be checked with a obd scan free at Auto Zone or Advance Auto Parts.
this is a comon problem on chevy 00-06 models a computer ground ,it seems ok at sight but inside it's just holding a few wires ,get under the car on the driver side passenger there you should find a two ground wire goin to the block a big, and a small ,the small one gets coroded try to fix it and let me know how it goes ok.
replace your MAP sensor(manifold absolute pressure) the map sensor is the computer for your fuel pressure regulator telling how much pressure. Unless your tahoe runs like **** going up hill than it inevitably your fuel pump
My problem was solved when I repaired my 4 wd activation dash switch. The switch was contacting on 2WD & 4HI at the same time. The front differential activation is vacuum activated possibly creating a tug of war that didn't actually engage it but drained off vacuum from the engine? A theory at best but stumbbled across it because I knew the switch wasn't working properly I repaired it and low and behold rough idle disappeared and all is good for 3 weeks running.