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  1. #1

    Question 98 5.7 Vortec Problem with Codes 174 and 172

    hello.need help please engine running rough change plugs wires,clean maf sensor twice new filter fuel and air. cleaned carburater with carburator cleaner still running rough added fuel treatment. noticed when had breather off that the carb. filter gasket has rubber gasket looks like one seal ring is damage but fits snug. sometimes light goes off and runs fine.

  2. #2


    How many miles does it have on it?

  3. #3


    That is an interesting pair of codes. According to my code list, P0172 is rich on bank 1 contrasted with P0174 which is lean on bank 2.

    Interestingly, my first thought with this pair is: Is it at all possible that, when some recent work was done, that someone somehow managed to "cross" the wires to the upstream O2 sensors.

    One correction to your post -- there is no carburator on these (unless someone has dropped a much older system onto the engine). I'm assuming that you are referring to the part of the air intake that attaches to the top of the throttle body. It might be worth the time and effort to look at that gasket. An air leak at that point, if large enough, can throw the air/fuel mixture off, which is exactly what your codes are pointing to.

    One good way to "see" inside what the engine is doing is to inspect the spark plugs. When you changed the plugs, did you note the condition of each one? In particular, were there indications on the bank 1 plugs that that side was indeed running rich? Indications that bank 2 was really running lean?

    Do you have access to a scanner? It might be useful to extract any freeze frame data from the computer. I might then clear the codes, then test drive it and see if both codes come back, or if one or the other only comes back.
    '98 K1500 Suburban LS 5.7 L 4L60E NV246 ARB
    '92 Ford Explorer XLT 4x4 4.0 L A4LD BW13-54 Trac-loc rear
    "My toys were the greasy cogs and springs and pistons that lay around all over the place, and these, I can promise you, were far more fun to play with than most of the plastic rubbish children are given nowadays." Danny in Roald Dahl's Danny The Champion of the World

  4. #4


    thanks for reply, yesterday fuel pump went out low pressure. replaced today and runs better but still rough idle and check light still on havnt checked codes yet will see about gasket tomorrow. I live in the country and its 40 miles to gm dealer. thanks and will let you know

    - - - Updated - - -

    320k on truck but motor has about 120k replaced fuel pump today and still rough idle and ck light still om

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