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  1. #1

    Default A Hard Shift and A Little Lope

    Hi guys,

    Well it's been a while since my last post, but I have been under the hood almost every weekend cleaning and changing parts. The stuttering problem seems to have been resolved when I changed out the idler pully. I noticed the old one wasn't sitting in the right spot and kept slipping. Since the new one has been on there haven't been any more "stuttering" issues, but now I have encountered something new.

    Background:
    Along with the idler pully, I also replaced the tensioner pulley by the water pump. (I think that belt goes from the water pump to the A/C compressor? Am I correct?) I also put a new cover on my after market K&N air filter (it looks like a cone). The cover is completely open on the side where the air flows in, about 4" from the inside of the fender, and has about 1/2" room around the filter itself before it meets the MAF on the other side. I have new plugs and wires and a new fuel filter. I have run numerous bottles of fuel injector cleaner through the tank and a bottle of sludge cleaner mixed in with the oil.

    Now, all that being said, I really don't think that what I have done so far would have created my current problem, but as I have stated before I am new to this and I haven't been under the hood this much in a long time.

    The current problems:
    1) I have a very hard shift from first to second gear when I push the truck to accelerate. If I baby the gas then it shifts normally. If I'm pulling in to traffic and need to accelerate quickly, the truck litterally jumps when it shifts from 1st to second. After that it shifts into higher gears smoothly, but is very sluggish and seems to be over reving to get into 3rd and 4th, shifting around 2000-2500rpm regardless of whether I am trying to accelerate quickly or slowly.
    2) While I'm driving at a constant speed, probably between 40-50 mph, it starts to lope (if that is the correct term). It feels like it is losing power and then recovers very quickly. I think it may be starving for fuel?

    Additional Info:
    I have checked the pressure by pushing the nozzle thing on the engine block and it sprays like it has plenty of pressure. Is there something that I can use to determine what the actual pressure is? What is it supposed to be?

    I look forward to your responses, thanks for the help!

  2. #2

    Default

    You can rent a fuel pressure gauge from autozone for free. They just take your creditcard info incase you do not bring it back. You screw it on the fitting and start the truck. I believe that the pressure should be between 50-60 psi but I could be wrong.

    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)

  3. #3

    Default

    Quote Originally Posted by Pikey View Post
    You can rent a fuel pressure gauge from autozone for free. They just take your creditcard info incase you do not bring it back. You screw it on the fitting and start the truck. I believe that the pressure should be between 50-60 psi but I could be wrong.
    Thanks! I will have to check that out. What do you think about the problems that I'm having? Do you think it is starving for fuel? Or could it be something else?

  4. #4

    Default

    This is my take on your second issue. I had the same issue while cruising between 50-55 mph. When I try to accelerate from 55 mph, it jerks back and forth as if it was starving for fuel or missfiring. It will not speed up above 60 mph unless I turn the a/c off.

    I just did a fuel pressure test on my 2001 Suburban. I had to buy the tool from Advance since they do not rent the tool anymore. It took me almost a week of elimination to come to a conclusion that my fuel pressure regulator was the culprit. I was dealing with a fuel pressure below spec issue. I was only getting 44 psi and bleeds off to zero in 2 minutes. There are 3 sources of fuel bleeding off. Injectors, regulator and check valve in the fuel pump. I found out my regulator was bleeding off fuel before I even got into the check valve on the fuel pump.

    As far as your first issue, I don't have any idea.
    2011 Chevy Silverado LT 4WD 30k miles
    2001 Suburban 2WD, 5.3, V8 185k miles
    1993 964
    1996 318TI

  5. #5

    Default

    Thanks for the help guys! I finally was able to check the pressure and it was at about 48 steady. I let the truck run for about a minute and it didn't change. How long should I leave the truck is running to see if it changes?

  6. #6

    Default

    From what I understand you should shut it off and see how long it holds the pressure

  7. #7
    Legend

    Join Date
    Sep 2010
    Location
    everett, massachusetts
    Posts
    1,487

    Default

    indicate what engine year and if its e85/regular fuel.

    on a gasoline 87 octane 5.3L engine 1999-2006 the fuel pressure should be 60-65psi key on engine off. if it rapidly drops off then you must check pressure at the fuel pump to see if its the check valve in the pump.

    with the engine running the pressure should be 53-60psi. I find 57 psi normal.

    e85 engines run on lower fuel pressure. 47-53psi .

  8. #8

    Default

    How do i determine what the engine year is and whether it is e85?

  9. #9
    Legend

    Join Date
    Sep 2010
    Location
    everett, massachusetts
    Posts
    1,487

    Default

    what model year is the vehicle ? using the vin # check with the dealership if its e85 capable. look at the gas cap IF OEM see if it says e85 fuel .

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