rough idle 4.3 v-6

Discussion in 'GM Powertrain' started by RATRODKING, Apr 27, 2010.


    RATRODKING Rockstar 100 Posts

    i have a 2003 s-10 extreme with 4.3 v-6 and automatic. i am the original owner.
    truck has 63k miles.
    everything is original, plugs, wires, rotor, cap, pcv valve, fuel filter, etc.
    on my way home from work today it started a rough idle at a stop light. had to put it in neutral and rev it a little. putting it in gear almost stalls it, but when i hit the throttle and get under way, it clears up about 90%.

    i will try changing the fuel filter hopefully tomorrow. to relieve the fuel pressure, all i have to do is take the gas cap off ?
    if, after the fuel filter change it still runs rough, i will take it to my mechanic to diagnose. there aint no way i am going to tune it up, since everything is real hard to get to, especially the drivers side plugs.

    would like to see what you guys might think it is ?
    thanks much.

  2. silveradotrailblazer

    silveradotrailblazer Epic Member 5+ Years ROTM Winner 5000 Posts

    Although your truck has low miles for a 2003 it has time on it, 7 years. Parts get old and brittle under the hood. I would change the fuel filter, plug wires, plugs and clean the throttle body and intake. Seafoam shows how to clean your intake on there website. Also I would change the cap and rotor. If you do this yourself it shouldnt cost alot.
  3. murdog94

    murdog94 Epic Member 5+ Years 5000 Posts

    Also remove and clean the IAC since the seafoam wont get that far up the intake.. Plus buying some MAF sensor cleaner and cleaning it would help as well..

    RATRODKING Rockstar 100 Posts

    thanks much guys..

    what is the IAC ? i am lost on these newer trucks. how do i remove and clean it ? also, where is the MAF sensor, and how is it cleaned, with special cleaner ?

    i was trying to take the cap off to look at the bottom side, but the dang torx headed screws are on there pretty tight. i know my patience, and there is no way i will attempt to change the spark plugs. there just aint no room there.
    i will check the seafoam website and see what there is there.

    oh, when i go to change the fuel filter, is there anything special i need to do to relieve pressure, or just remove the gas cap ?

  5. wis bang

    wis bang Rockstar 100 Posts

    It's still a PITA but your symptoms sound just like a carboned EGR valve. Almost won't idle but runs fine 'cause the plunger in the EGR isn't closing when the throttle closes.

    First time i curred it w/ Seafoam thru the brake booster vacuum hose...

    Second time I had to pull the EGR and break out the ring of carbon that surrounded the plunger and prevented it from closing...

    The EGR valve is only supposed to let exhaust gas flow into the intake when ther are sufficient RPMS to burn them...that's why your problem goes away above an idle.
  6. murdog94

    murdog94 Epic Member 5+ Years 5000 Posts

    Idle Air Control valve....

    RATRODKING Rockstar 100 Posts

    thanks guys.. when i get home from work today i will look at both the egr valve and ilde air control valve, and see how hard they are to get at.
    where is the idle air control valve located ? on the throttle body or the mass air flow thing ?
    like i said, on these newer computer cars and trucks i am lost.
    thanks again.

  8. murdog94

    murdog94 Epic Member 5+ Years 5000 Posts

    The IAC is on the throttle body... Also you are doing a tune up correct??? Also is the check engine light on???

    RATRODKING Rockstar 100 Posts

    ok guys.
    drove my other truck to work today, came home and fired up the s-10. it was running perfect. drove it around for 15 minutes and it started running rough again, so i took it to autozone and had them put their computer on it. it said # 5 cylinder is miss firing.
    popped the hood once again, looked at how hard it is to tune up, and decided to take it to my mechanic. he will look at it tomorrow.
    i will let you knwo what he finds.

  10. murdog94

    murdog94 Epic Member 5+ Years 5000 Posts

    Fuel Pressure regulator. id place a bet it is.

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