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  1. #1

    Default 2002 GMC Yukon XL running rough

    Our 02 Yukon XL with the 5.3 flex fuel model runs rough at an idle sometimes, then others it idles high and going down the road sometimes it feels like its skipping. The problem is that it doesnt do it all the time, it comes and goes which is making it hard to find the problem. We have 150,000 miles and have done the following:

    replaced fuel filter

    replaced intake gaskets (there appeared to be a leak)

    added fuel injector cleaner (twice)

    My friend who is a mechanic, has a diagnostic tool and he keeps getting alot of misfires from various cylinders, but more misfires seems to be coming from cylinder #2. He also gets a O2 sensor code.

    Any ideas? Thanks to all in advance!

    John

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    I should also note that we put a fuel pressure gauge on and it reads steady at 45-50.

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    spark plugs have about 55,000 on them, wires have only about 20,000 miles on them. We did exhaust manifold last year because some of the bolts were broken.

  2. #2

    Default

    That fuel pressure number is low for that truck. Should be in the high 50's at idle.

    1996 Chevy Tahoe LT 5.7L V8 4X4 205,000+ miles. Built proudly at Janesville Assembly in Janesville, Wisconsin
    Basic mods: Lights all over, bunch of electrical work, and a couple cooling mods.

    Check out my other mods in My Garage: http://www.gmtruckclub.com/forum/sho...t-Tahoe-4-Door

  3. #3

    Default

    Do you think it could be the fuel pump or fuel pressure regulator?

  4. #4

    Default

    Those are the normal culprits. Fuel pressure regulator is fairly easy to replace so you should try that first.

    1996 Chevy Tahoe LT 5.7L V8 4X4 205,000+ miles. Built proudly at Janesville Assembly in Janesville, Wisconsin
    Basic mods: Lights all over, bunch of electrical work, and a couple cooling mods.

    Check out my other mods in My Garage: http://www.gmtruckclub.com/forum/sho...t-Tahoe-4-Door

  5. #5

    Default

    Just to ad some more info, i took it for a spin this afternoon and the problem gets worse going up a steep mountain road. The engine almost cuts out, bucks and jerks, think i might have whiplash! Just kidding about the whip lash, but you get the idea.

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  7. #6

    Default

    If you pull the vacuum line off of the regulator and fuel comes out then your regulator is bad. It is located on the fuel rail on the top of the motor on the driver side, right around the middle of the fuel rail. You may have to pull the Vortec cover off to get to it.

    1995 Silverado 4x4
    6" BDS Suspension Lift-3" Body Lift-Add A Leaf in rear -Trailmaster SSV Shocks-Duel Steering Stabilizer Kit -AirAid Cold air intake-
    4.56 Gears with Detroit Auburn Locker-Pro-Comp Traction Bars with duel shocks-Aluminum Skid Plate Kit-38.5" x 16.5" Mickey Thompson Baja Claws-Constant Dropping fuel gauge

    2005 Yukon XL Jet Power Programmer, Bilstein Shocks, Bilstein rear springs, Helwig Anti-sway bars, EGR Window Visors, EGR Hood Shield, Denali Headlights, Headlight harness upgrade, GE NightHawk Bulbs, White Night Rear lighting system, Russell Braided SS brake lines, PowerStop Brake pads, PowerStop cross drilled and Slotted Rotors, http://www.gmtruckclub.com/forum/sho...5-GMC-Yukon-XL
    2002 Silverado ext cab 2wd (Sold)
    2003 Yukon XL (Totaled)

  8. #7

    Default

    I pulled off the vacuum line and no gas game out, but i have read that it could still possibly be bad? Am i wasting money by replacing it?

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    So i replaced the fuel pressure regulator and one of the upstream o2 sensors (parts store only had 1) and still have the same problem. The engine seems to run smoother going up hill when i really get after it? I'm really getting frustrated! I don't have money to keep replacing parts and not solving the problem. Any suggestions or recommendations any one???

    - - - Updated - - -

    i borrowed a diagnostic code reader and got the following:

    P1639 - 5-VOLT REFERENCE B CIRCUIT FAULT
    P0300 - MULTIPLE CYLINDER MISFIRE
    P0332 - KNOCK SENSOR CIRCUIT LOW BANK 2
    P0452 - EVAPORATIVE EMISSION CONTROL SYSTEM PRESSURE SENSOR LOW INPUT

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