High Altitude Emissions-Utah Sub now in CA

Discussion in 'Chevy Suburban Forum (GMC Yukon XL)' started by Jeff21, Jun 14, 2012.

  1. Jeff21

    Jeff21 New Member

    Hi All,

    This is my first post not counting my "new truck" one. I am about to take our 94 Sub 5.7 4x4 1500 in for a CA smog test for the first time and I decided to do what my daddy taught me and work on my own vehicle. I would like to get the Sub in top running shape before testing. We have owned the truck for over a year and have averaged 10 MPG in it. It does not seem to matter if we do all city or half hwy, it always gets 10 MPG. There seems to be top end wear with oil burning when it starts. It has 161k on it. I just pulled a spark plug and it looks good, but has a lot of oil on the threads. My experience with working on cars ended in the carb days and don't have a clue about my truck's fuel delivery. I still have the original window sticker and it reads "High Altitude Emissions - NO CHARGE" under the options. The Sub was originally purchased in Utah and we bought it from the family that brought it out to California.

    My questions are:
    1. What is high altitude emissions and is this something I need to be aware of before I smog?

    2. It says my 94 has EFI and to be specific TBI from the Chiltions manual. Can you look at the attached pics and verify?

    3. It is in good basic running shape, it gets poor MPG, any thoughts on steps to do a good tune-up before smog? No smog work done and it looks like the last tune up 75k ago but likely sooner (due to incomplete records). Does not seem to burn oil after running a bit.

    Thanks! Jeff

    Attached Files:

  2. Joeairforce

    Joeairforce Epic Member 5+ Years 100 Posts

    #1. It's tuned a little different to make up for the thinner air at the higher altitude.... I wouldn't think it should matter.... but then again I don't have to worry about emissions testing...

    #2. Yes it is.

    #3. It sounds to me like the burning oil only at startup could possibly be leaking valve stem seals.... Could be something else too but that's my guess...

    As for the low mpg... I would go through everything real good and make sure all the filters/fluids are good and check to make sure there's no dragging brakes. How's the transmission fluid look/smell? How does it feel when shifting?

    If it was my truck I would (if you haven't done this already) replace all the spark plugs with properly gapped AC Delcos, replace the wires/cap/rotor, and fuel and air filters.

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