Need insight from a 4.3 person

Discussion in 'Chevy Silverado Forum (GMC Sierra)' started by a.graham52, Nov 14, 2012.

  1. a.graham52

    a.graham52 Rockstar 100 Posts

    Ok so here's the deal: bought a 2002 Sierra with a 4.3 and a 5spd.

    I've done spark plugs, wires, cap and rotor and fuel filter. And my long term fuel trims are around +10 with a 14% throttle position. Fuel economy is around 15-16mpg. I did check my PVC hoses and they are well attached. I'm using and Altra-gauge for all my figures. I'm going to verify fuel trim readings with a tech2 from work. I have had the Altra-gauge in my alero for about a year and seems very reliable. Is these fuel trims normal or what?
  2. Revredneck

    Revredneck Rockstar 100 Posts

    Those numbers are well within the range of normal. As long as it's running well and the mileage isn't changing, you're okay.
    Good Luck and God Bless
  3. a.graham52

    a.graham52 Rockstar 100 Posts

    well i guess im just kinda bummed that my old 85 sierra with a toilet bowl powered 4.3 got better gas millage and with 2 less gears! i got 16mpg with that thing without trying, im lucky to get 14.5 with my 02 these last two tank fulls.

    not only that but i did try this. i unplugged the MAF sensor so the ecm was put into speed density and test drove it. fuel trims went down to 0 and operated like i normaly see on other vehicles. i then used a smoke machine attached to the oil dipstick to introduce smoke into the the block/valve covers/intake etc. i found smoke coming out around the dizzy gasket. last weekend i did intake gaskets (didnt help fuel trim numbers any but i had a coolant leak anyways). so from there i plugged both sides of the pcv system and reset the fuel trims with a tech ii. no difference. and verified that unplugging the maf sensor brought long term fuel trim back to zero. i also put RTV around the intake tube where it attaches to the throttle body. still doesnt make any difference with the MAF plugged in. i did some home work and the highest fuel trim number (before the ses light comes on) is +25. im pretty much half way there and i havnt even added the high flow air filter, headers and exhaust im planning on.
  4. You've bought one best 6 cylinder motors I know of. When maintained one will easy go above 200000 miles. I've heard of them going 300000 miles.
  5. j cat

    j cat Epic Member 5+ Years 1000 Posts

    with my 1983 I used to get 23 MPG. then when they changed the fuel [gasoline] to the new type which reduced emissions the MPG droped to 18MPG .

    that was many years ago . with the fuel today carbs do not last long with the alcohol. rubber parts don't last long on these old vehicles.
  6. a.graham52

    a.graham52 Rockstar 100 Posts

    yeah im aware of how the new fuel effects economy. i stopped driving my 85 a year ago so that had e10 going through it all the time.
  7. j cat

    j cat Epic Member 5+ Years 1000 Posts

    this summer I had a e85 capable chev. with the MPG display it was quite clear though e85 is cheaper you get what you pay for in BTU output per gallon as the E85 did cause lower MPG.

Share This Page

Newest Gallery Photos