Chevy silverado surge at rough idle

Discussion in 'Chevy Silverado Forum (GMC Sierra)' started by jteuban, Jul 16, 2011.

  1. jteuban

    jteuban New Member

    Hello, I am asking this for anyone who might help me with this situation. I have a 1995 Chevy silverado that when you hit about 900-1000 RPM, surges like if you are pulling out or in a driveway or backing out only when going slow but after you hit 900 RPM it runs great. Rough idle is terrible. I dont understand it has a throttle body could it be a problem with that or a throttle pos sensor, egr valve, sock in fuel tank. even a rotor cap or distributer prob. timing? Oh someone help with this PLZ.
  2. stephan

    stephan Rockstar 4 Years 5000 Posts

    Not sure if I understand this correctly, but you say it runs both good & bad at 900 RPMs???

    This could be any of the things you mentioned above, & a few more,,, Need more info. When was your last service, last tune up. Ever had any service work done to it since you've owned it?
  3. jteuban

    jteuban New Member

    Oh ok well it runs fine at idle and then when you go to accelerate it hits 900-1000 and it surges, it kind of sounds like the engine is gasping for air it almost cuts out and then comes back when you speed up past 900 or when you come to a stop sign and sometimes but not very often it almost cuts out and then comes back. Im thinking its a vacuum prob like a map sensor or even a trott pos sensor. And you it is serviced on a regular basis I do my own mechanic work. It could also be a bad place in the distributer idk thanks for the reply.
  4. stephan

    stephan Rockstar 4 Years 5000 Posts

    How does this run at higher RPMs? At freeway speeds does it run smooth & have lots of power, or does it miss, stumble & surge there too. Any power loss up there or any miss? If it runs fine up there, then you can eliminate a few of those things like the fuel sock, fuel filter, fuel pressure, & possibly even the spark plugs, wires & distributor.
  5. jteuban

    jteuban New Member

    The truck runs great after that, It just like it hits a bad spot. Im thinking of replacing the dist cap and rotor button to see if it makes a diff. Last year I cleaned the egr valve and it seemed to fix the prob for a while so idk but at the same time i acc left off the vacc line to the map sensor but when I put it on it did the same thing could this be the problem? It has been doing this for a long time so IDK? help, cheers

    Oh also the truck is chipped could this pose a problem? Can I adjust it like the idle speed and fuel delivery???
    Last edited: Jul 18, 2011
  6. Jbumpus

    Jbumpus New Member

    I had similar issue with my 02 silverado. I ended up replacing the cap twice and the rotor once. After it started acting up i replaced the whole distributor. Relatively easy install. Set TDC and align it up. When i looked at my old distributor the helix gear fins that meshed up with the crank had been half crushed/compressed and was causing it miss-fire and run rough on normal / hard acceleration. It ran fine at idle and coasting on the highway.

    Hope i have helped.

    Last edited: Jul 18, 2011
  7. jteuban

    jteuban New Member

    Thanks for the reply I was thinking of trying this along with new vacc lines to egr valve and map sensor I think I can hear a vacc leak somwhere I will look into that as well. Cheers
  8. kcfocus1

    kcfocus1 New Member

    Most likely it is throttle position sensor, the get burned out contacts in that rpm range.
    There is a simple test using a voltmeter that will eliminate this possibility. Good Luck!

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