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  1. #1

    Default Help, please rough idle

    Just put in the new spark plugs and wires as well as cold air intake. Was idling roughly before and immediately after the install all seemed well. This morning it was about 10 degrees out and I fired it up. Very rough idle, loud ping noise, I guess that's what misfiring sounds like? Revs were up and down, once I'm moving down the road it's fine. Come to a stop light and the revs dip again feeling like its going to stall. Sound like an idle air valve problem? Just bought the damn thing and the check engine light was on for the catalytic converters. So I'm not sure if the CEL is on now for something else.

  2. #2

    Default

    My guess is that its running lean... Hence the codes on the cats. Probably the MAS.
    2009 Chevy Silverado 2500HDLT 6.0L w/ Towing Package, Dick Cepek GM8 Rims, Dick Cepek FC II 33X11.50R17,RKSport Ram-Air Hood(Functional), Lazer Lite Aluminum Tonneau Cover, Road Armor Stealth Bumper, PIAA Lighting, Diablo Trinity Tuner, Diablew Custom Tune, BullyDog Cold Air Intake, American Racing Headers w/highflow cats, Corsa Performance Sport Exhaust, Custom Striping, Black Bowties front and rear, Fuel Grille Inserts, Recon Headlights, Readylift Shocks, Readylift Upper Contol Arms, 2" Blocks in the Rear..

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  3. #3

    Default

    The best approach is to pull the codes and come back here with each code (if there is more than one)
    Ray

    '09 Avalanche LTZ - Black
    '05 Envoy XL (sold)

  4. #4

    Default

    If you have the codes, check out obd-codes.com and ask here, someone will be able to help you.


    2010 Silverado Z71

    Kyle-USAF-MI/VA

    "Fueled by Haters"

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    | Custom tune | Cam | Stall Converter

  5. #5

    Default

    Yes get the codes... This will verify. I am guessing lean as it would be rare for the two to be tripping otherwise. I have a feeling it will be lean on bank 1 and bank 2. This is what my sons truck did when is MAF failed.

  6. #6

    Default

    Banks 1 and 2 both running lean. Just had it read at AdvanceAutoparts.

    Just put on the new intake, could it be the computer needing to be reset? Only happens in the morning, after driving it for 10 mins and getting it up to operating temp it runs just fine...

    - - - Updated - - -

    Just refitted the air intake, unplugged the battery to reset the computer, and replaced the PCV. Guess we'll find out tomorrow morning if that helped anything. Keep you guys posted

  7. #7

    Default

    The PCM controls the air/gas mixture when the engine is cold, as it warms, the control is switched to the O2 sensors. The O2 sensors are changing the fuel mix so the engine will run smooth. A fuel delivery program, in the ECM, provides the injector info while the engine is cold, sounds like it is an air problem.

    Take a 2nd look at TinTom64b 's suggestion.

  8. #8

    Default

    Update:

    fired it up this morning after refitting the intake, replaced the PCV, and unplugged the battery. Much smoother but still not where it should be. So maybe the MAF has gone bad? Is there a way to test that before purchasing?

    to be able to get the code for the MAF not working I would have to run the scan when the engine is cold, correct?
    Last edited by kinson33; 12-12-2012 at 11:26 AM.

  9. #9

    Default

    This just a problem at idle, or does it run like crap all the time? Pull the codes before buying anything. It sounds like an Idle Air Control valve to me.Try to clean it. You might also take a look at your throttle plates. They get really cruddy after a while and can cause bad and erratic idling too.

    Kinson, you want to scan the vehicle after it goes into closed loop mode. If it has set a code, you can read it when the engine is cold, but it is best to let it warm up so you can look at the data while it is running.
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  10. #10

    Default

    Quote Originally Posted by moogvo View Post
    This just a problem at idle, or does it run like crap all the time? Pull the codes before buying anything. It sounds like an Idle Air Control valve to me.Try to clean it. You might also take a look at your throttle plates. They get really cruddy after a while and can cause bad and erratic idling too.

    Kinson, you want to scan the vehicle after it goes into closed loop mode. If it has set a code, you can read it when the engine is cold, but it is best to let it warm up so you can look at the data while it is running.
    Runs great after it warms up which leads me to believe its the MAF as suggested since it switches to the o2 sensors after getting to operating temp.

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