no power and horrific mileage in my k2500

Discussion in 'General Chevy & GM Tech Questions' started by younggun, Jan 19, 2012.

  1. younggun

    younggun New Member

    Any help would be appreciated. Bought this truck from a farmer friend who owned it for the last 16 yrs. It is a 1995 K2500 4x4 with the 5.7 and 4l80 trans. the truck was ordered with 4.10 gears.

    now on to the problem..... this truck had a bad miss, no power and poor fuel mileage(8.9 mpg). I took it to two different shops they ran diagnostics and couldnt find the problem at either place, no engine light or stored codes at this time.

    I have replaced the following- plugs wires cap and rotor, air filter, fuel filter, fuel pump, pick up coil in the distributor, also checked the gear on the distributor. this got rid of my misfire problem and seemed to help the engine start easier and run smoother. I then removed the cat. converter and installed a thrush welded muffler with new pipe to the factory exit. o2 sensor tested ok. still no power and bad mpg so I replaced the ecm, still no improvement.

    I have tried swapping out the egr valve as well as the injectors, I tested the iac valve on the throttle body and cleaned it as well. coolant temp sensor is reading ok under diagnostics at the shop. so I am at a loss on this one. The truck just has no low end power at all and is still getting 9.5 mpg after all the work i have done thus far. I have owned this style truck in the past and theyt always ran well and got decent fuel mileage but this thing is a slug and eating me alive in fuel. any ideas??????

    ---------- Post added at 01:30 PM ---------- Previous post was at 01:27 PM ----------

    Almost forgot I did find a caliper hanging up up front recently and thought I had found my power and mileage issue but I replaced the calipers, rotors, and pads a couple of weeks ago and although it no longer feels like I am towing a trailer it still has no low end and gets 9.5 mpg!!
  2. dpeter

    dpeter Epic Member 5+ Years 500 Posts

    Way oversized tires? Have the compression on the cylinders checked and recheck the timing. Also ask previous owner if timing chain or cam work has ever been done. If not timed or set up correctly it can run OK but not not run as it should. How many mile on truck?
  3. younggun

    younggun New Member

    265/75/16 mud and snow tires, 123000 miles on the truck. checked the timing and re checked it after installing the pick up coil. nothing has been done to the timing gear set, could this be the issue?
  4. vncj96

    vncj96 Epic Member 5+ Years 1000 Posts

    I would suspect its an internal engine problem and it may not have a code for it. Does yout truck throw black smoke out the tailpipe? I had a bad exhaust valve on my suburban and we couldnt figure it out until we ran a compression check and scoped all the valves. Never had a light come on either. Although you should have plenty of power with the 4.10 gears I wouldnt expect much more for MPGs though. Have you checked the tranny at all?
  5. younggun

    younggun New Member

    no smoke and it doesnt burn oil either. has had synthetic shaeffer oil in it since new. the previous owner said it always had a ton of power and averaged 14 or so mpg? haven't had a chanhce to take it to the tranny shop yet but it definately shifts soft.
  6. younggun

    younggun New Member

    took the truck to the tranny shop, went for a ride with the owner, he says trans. is a little lazy but shifting as it should and not showing signs of slipping or anything like that. He couldn't believe the truck had 4.10 gears said it drives like it has 2.38 under it, lol no kidding buddy thats why I am ready to send it over a big hill somewhere!!!
  7. vncj96

    vncj96 Epic Member 5+ Years 1000 Posts

    Did you get a compression check yet? What kind of spark plugs did you put in it, these vortecs DO NOT react well with non OEM plugs. When I bough my suburban it was getting 13 mpg and did a tuneup and put back in the OEM iridium plugs and it brought it back to 16mpg. Many others on here have the same results...
  8. HippyD

    HippyD New Member

    r u dragging the front running gear around or do u have a sure way to make sure the axles are disengaged, under a no load condition the engine should be snappy when u hit the gas. if its not then u have an engine problem, could be starving for fuel. bottomed my tank out and mashed it up against the fuel pump pick up. thats about the mpg i got when i dragged the front around. took it a minute to get rpms up until the tank was fixed
  9. younggun

    younggun New Member

    how to I check to see if I am dragging the front running gear? I know that when the truck moves so does the front drive shaft all the time, is this what you mean? it isnt actually in 4wd because in loose stone only the rear tires spin but I am intrigued as to why the transfer case seems to be turning the front drive shaft, not real familliar with these newer style 4x4 systems so I wasnt sure if that is normal or not.
  10. rileyjr16

    rileyjr16 Epic Member 5+ Years 1000 Posts

    Front driveshaft turning is normal in 2wd.

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