Poor MPG and Lacks power

Discussion in 'Performance & Fuel' started by snowmen88, Jan 4, 2010.

  1. snowmen88

    snowmen88 New Member

    Hi Everyone,

    I have a 97' Chevy Silverado ext cab
    4.3lt Vortec with 72k
    Tires: 265/75/r16 max size for truck Stock was 245/70/r16
    Exhaust: 1-cat, 1-glass pac and 2-20" tips. Backpressure tested good.

    The problem that I have had for several years now is poor MPG, 11 city and 14.5 HWY. I was get'n 19/23. Also, the truck lack the "get up and go" it once had. Had the truck to the dealership and put on a TechII twice and all readings are within spec. I will list the thing I have replaced to save time. All parts replaced with OE.

    New: distrib, cap, rotor, plugs, wires, fuel pressure reg (x2), fuel pump (soon to be x2), fuel filter, tranny, alternator, EGR, pcv, all the O2 sens, therm stat, air and oil filters done per schedule maint. Thats all I can remember.

    Some stuff listed broke and needed replacement but I listed it any way.

    Dealership is pointing at my tires and glass pac. Tires I can see for some drop but not that much. Their saying the glass pac is not giving enough back pressure to heat the sensors up so the truck thinks it's running cold and is dumping more fuel. My front hubs are bad and I unpluged the ABS to bypass but that would have no effect.

    Any feed back you guys can offer to end my nightmare would be great. Thanks for your time!
    Last edited: Jan 26, 2010
  2. TritonBoulder47

    TritonBoulder47 Rockstar 4 Years 500 Posts

    The main problem is that you have a V6 in a full-size truck...

    The things I would try are getting an intake and a programmer... That should help with both your lack of power and MPG... Also your bad MPG might be due to a miscalculation... Your tires that you have installed now might be a different overall diameter then the stock ones, thus throwing off your speedometer and your odometer... A programmer would solve that problem aswell...

    Hope this helps... :great:
  3. snowmen88

    snowmen88 New Member

    Do you mean like a K&N air intake?

    The tires are due for replacement. I'm going to put the stock size back on. I'm also removing the glass pac and replacing with the OE muffler. As far as the programming I will have to find someone in the St. Paul area with a programmer and pay them to do it. I want to see if the muffler and tires make a differance.

    "The main problem is that you have a V6 in a full-size truck... "

    Yeah it's V-6 but it had more than enough power for what I hauled or towed. Plus, I bought it new and bought it for 13K less then sticker. Great deal!
  4. Chevyboy96

    Chevyboy96 Rockstar 4 Years ROTM Winner 100 Posts

    Nicely Put Triton :great:

    Yes a CAI- K&N, S&B, AirRaid, etc.
  5. snowmen88

    snowmen88 New Member

    The front hub assem with the front wheel speed sensors. I tried just sensors but didn't work. I needed to replace the whole assem.

    I want to say things changed in 02'-04'. Thats right about the time the fuel pressure regulator, tranny, tires and exhaust where done.

    Sunday, I had the whole day to myself and I got both front hub assem, rotors, brakes, fuel filter and feul pump replaced. Took it for a test drive and i'm not sure yet (need to drive some more to be sure) but I think the aftermarket fuel pump might have been my most of my issue. It was 2AM when I went for the test drive but I think it has alot more power, acceleration and it lites up right now.

    Get back to ya with an update when I know for sure.
  6. snowmen88

    snowmen88 New Member


    Well, I put a new WIX fuel filter, replaced the defective fuel pump with a OE delphi , installed a K&N air filter and went back to the stock tire size (245/75/R16). Filled the tank and went for a drive. Went 50 miles and used just over a 1/4 tank of gas. I am so upset with this truck!!!

    If anyone knows how torch a truck and make it look like an accident - please drop me a line!!!!!
  7. vncj96

    vncj96 Epic Member 5+ Years 1000 Posts

    My suburban gets the same mileage, so there has to be an issue that you cant find. I know plenty of people with fullsize trucks and a V6 and pull 20+mpg. have you had a compression check done at all?
  8. judsteele

    judsteele Rockstar

    ya know one of the guys at work has a 5.3 and he gets better mpg then me!! i have a 4.3 full size silverado 4x4 mines really stock, exp i have the k&n cai, the winter i really get the worst mpg.. i hope you find out what the cause is......but its still a LITTLE better then what your getting.
  9. Stealth

    Stealth Epic Member 5+ Years 1000 Posts

    My dad works in a glass company that has done most of the buildings in downtown Salt Lake City, and they use GMC work trucks. what he was finding is that the V6 trucks get about the same gas mileage as V6 trucks even unloaded, so he switched over to buying V8 trucks that can actually haul trailers.
  10. snowmen88

    snowmen88 New Member

    To the best of my knowledge a compression test has not been done. I have thought of that and it is on the "NEW" list of crap to check out. This truck did get 20+ mpg but I just can not remember when it all went down hill.

    1.) Compression check.
    2.) Verify the right tranny was put in 5+ years ago.
    3.) Possible problem with 4x4 tranfer case. Possibly causing resistance.
    4.) Smoke (or low pressure and dish soap) the intake and look for leaks.
    5.) Change out the cat.
    6.) Drive off cliff into Mississippi and claim stolen the next morning.

    If you guys have any other suggestions that I might have missed PLEASE let me know.

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