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  1. #1

    Default Fuel delivery problem on '95 TBI

    Hi everyone! My 1995 5.7L TBI seems to have a fuel delivery problem. Looking for suggestions as to what it could be.

    I've noticed a real lack of fuel mileage lately (used to get around 14, now only 10), and a pronounced loss of power at the upper end. I had the air filter off and the motor running, and noticed a lot of gas being fed to the throttle body. The air baffle plates were almost closed at idle, and you could see the gas on them (they were wet). The fuel regulator also had a lot of varnish on it, and was wet with gas also (not a lot of gas, but you could see it). You can smell gas in the air filter also.

    Anyone think this might be the fuel pressure regulator, or maybe one of the sensors (IAC, Map, etc.)?

    Any help is greatly appreciated!

    1995 GMC Suburban 5.7l SLE

  2. #2
    Jr. Engineer
    Join Date
    Feb 2007
    Edmonton, Alberta, Canada


    generally I belive this is normal as my truck runs similar.

    without a air/fuel meter its hard to tell... but id honestly look at ignition for top end explosion more.

    1993 K1500 Suburban 350TBI, 378,486KMS on frame, 49,000KMS on Drivetrain. Lots of mods, built for haulin trailers and haulin @$$ :)

    2000 K2500 Yukon XL 6.0L Vortec 252000KMS custom CAI, and exhaust...but not done yet.

    "If you are dumb enough to do something you don't know how to do, and can't do it safely then WHEN you get hurt its your own fault...BONEHEAD"

  3. #3
    Legend unplugged's Avatar
    Join Date
    Sep 2006
    High Deserts of SoCal


    What does the color of the residue in the tailpipe look like? Black soot would indicate a rich mixture. High fuel pressure wouldn't necessarily cause poorer mileage as long as the gas is being burnt. Raw gas into the exhaust will cause premature failure of the cat converter. Smelling any rotten eggs lately?
    There is no way to happiness....happiness is the way.:yipi:  _vXMYypuKMJFw671uF2ZPhjez_j-atRmcjM2zQKpQi1JSsB75/burb1.JPG
    High Desert SoCal
    93 K1500 burb (personal) 350 AT 3" Lift 250K+
    02 Honda Civic LX
    Looking for a 1990's Miata for an engine swap

  4. #4


    How long since a full tuneup? AC Delco plugs, cap, rotor. Napa Premium wires. Fuel and air filter.
    When you hear hoofbeats, look for horses not zebras.

  5. #5


    Thanks for the replies! I just changed the cap and rotor and put on new plug wires and plugs. Air filter was just a month old, and I changed the pcv valve. There was some rust on one post on the distributer cap (#3 hole), that could be causing some problems!

    I have a fuel filter, just have to find time in the next few days to install. Haven't had a chance to test the upper end power yet. Hopefully it's back!

    Would it be a good idea to pull the IAC and clean it, and also the EGR valve and clean it and the ports?


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