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  1. #1
    Jr. Apprentice
    Join Date
    Mar 2011
    Location
    Birmingham, AL
    Posts
    11

    Default 96 Sierra stalls when giving it gas

    Hello All,
    I bought this truck 3 weeks ago a 1996 GMC Sierra 1500 LS 4.3L V6 vin:W Manual Transmission for $500. Great deal in my opinion. The truck did not run so I trouble shot and found the the engine was not receiving fuel and the fuel pump did not have the "whirring" sound it should. I first replaced the FP relay but no go. Then I replaced the Fuel Pump, Assembly and Fuel Filter. Still the truck would not crank. So I changed out the spider injectors and finally the truck cranked for me. I was pumped until I tried to drive the vehicle and the vehicle tries to stall in Neutral when giving it gas unless you baby the accelerator.
    I drove it to Autozone to get them to tell me the codes. I got MAF sensor code, TPS (throttle position sensor) code and Random cylinder misfire. After this I changed the MAF, TPS, spark plugs and wires, the oil and flushed the radiator. (also I am going to change the thermostat because when I did run the truck for 20-30 minutes the temperature gauge never moved and the engine was seeming to overheat no smoking yet though).
    Also just a side note I did a compression check on the engine when I changed the plugs and all cylinders were 190.
    I am about ready to give up and take it to the mechanic but I thought I would try a forum to see what thoughts people may have.
    After everything the engine light did come back on yesterday after running the engine for 5 minutes and lightly revving the engine without stalling it, but have yet to check the codes.
    Sorry for the long 1st post! I appreciate any advice I may receive!
    1996 GMC Sierra LS 4.3L V6 VIN:W

  2. #2

    Default

    After replacing most of the fuel system, I'd probably put a fuel pressure gauge on it to make sure the fuel system is doing what it is supposed to.

    Do you remember what code numbers you got? I'd probably take those codes down to the library, pull out a good repair manual (usually Motor or Mitchell Engine performance and emissions troubleshooting) and look up the test procedure for each code.

    I might clear codes and then run it again to see if all the same codes keep coming 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

  3. #3
    Jr. Apprentice
    Join Date
    Mar 2011
    Location
    Birmingham, AL
    Posts
    11

    Default

    Thanks Mr.Shorty for responding. When I get home from work I'll try getting this stuff done. Don't have a fuel pressure gauge yet though. Any knowledge on what the fuel pressure should be?
    1996 GMC Sierra LS 4.3L V6 VIN:W

  4. #4
    Jr. Apprentice
    Join Date
    Mar 2011
    Location
    Birmingham, AL
    Posts
    11

    Default

    I went and bought a fuel pressure test kit and a code reader. Didn't get a chance to test the fuel pressure yet, but I did use the code reader. Now it says P0108 MAP system performance. Here is the Freeze Frame. (wished I had bought the code reader first instead of relying on Autozone)

    Parameter Description Value
    DTC for which Freeze Frame was Stored P0108
    Fuel System 1 Status Open Loop
    Fuel System 2 Status Open Loop
    Calculated LOAD Value 4.31 %
    Engine Coolant Temp 69.80 F
    Short Term Fuel Trim - Bank 1 0.00 %
    Long Term Fuel Trim - Bank 1 0.00 %
    Short Term Fuel Trim - Bank 2 0.00 %
    Long Term Fuel Trim - Bank 2 0.00 %
    Intake Manifold Absolute Pressure 27.83 inHg
    Engine RPM 323.25 rpm
    Vehicle Speed Sensor 0.00 mph
    Air Flow Rate Mass Air Flow Sensor 1.34 lb/min

    This was the only DTC to pop after running the truck for 10 min or so...lightly driving it around the neighborhood. Still the same issues with rough idling and stumbling and hesitating on acceleration.
    1996 GMC Sierra LS 4.3L V6 VIN:W

  5. #5

    Default

    It looks like the MAP sensor is reading too high (not enough vacuum). Is there a vacuum leak? Clogged exhaust?
    '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

  6. #6
    Jr. Apprentice
    Join Date
    Mar 2011
    Location
    Birmingham, AL
    Posts
    11

    Default

    Not sure about the vacuum leak or clogged exhaust. I looked up some things I could try to test the vacuum (spraying carb. cleaner on the vacuum hoses while the engine idles to see if it changes the rpms) but I didn't notice a difference. I'm strapped for cash at the moment but I might just get a shop to test this. I did take the truck for a spin today to see if I could get some more codes to hit and wouldn't you know they did. Here is the new report:

    MIL DTC
    P0300
    Multiple Cylinder Misfire Detected

    Stored Codes
    P0108
    MAP Sensor Circuit High Input

    P0122
    TP Sensor Circuit Low Input

    P0131
    HO2S-11 (Bank 1 Sensor 1) Circuit Low Input

    Diagnostic Information
    Freeze Frame Information

    Parameter Description Value
    DTC for which Freeze Frame was Stored P0300
    Fuel System 1 Status Open Loop
    Fuel System 2 Status Open Loop
    Calculated LOAD Value 17.65 %
    Engine Coolant Temp 64.40 F
    Short Term Fuel Trim - Bank 1 40.63 %
    Long Term Fuel Trim - Bank 1 0.00 %
    Short Term Fuel Trim - Bank 2 50.00 %
    Long Term Fuel Trim - Bank 2 0.00 %
    Intake Manifold Absolute Pressure 10.96 inHg
    Engine RPM 2,978.75 rpm
    Vehicle Speed Sensor 0.00 mph
    Air Flow Rate Mass Air Flow Sensor 4.91 lb/min

    So the TPS, MAPs and Multiple Cylinder misfire are showing. The new one I'm not quite sure what it is I'm guessing to do with fuel (P0131).

    I also noticed the MAP was only 10.96 in the freeze frame this time. I didn't clear the codes from last time I wonder if the MAP code was still logged in the computer and not something that happened this trip I took.

    I'm confused as ever.
    1996 GMC Sierra LS 4.3L V6 VIN:W

  7. #7
    Jr. Apprentice
    Join Date
    Mar 2011
    Location
    Birmingham, AL
    Posts
    11

    Default

    Well I figured my issue out. The distributor cap is marked 2,4,6 on the left side and 3,1,5 on the right..I stupidly ASSumed that it was marked 1,3,5..changed the wires and the fouled out plugs and she runs smooth as butter.

    Thanks for letting me run this by you guys!

    Next will be the 2002 Trailblazer sitting in the driveway. Loss of compression in the 2 cylinder. Wish me luck
    1996 GMC Sierra LS 4.3L V6 VIN:W

  8. #8

    Default

    Glad you figured it out. It can be irritating when little things like that sneak up on us.
    '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

  9. #9
    Newbie 97GMCJimmyHHREdition's Avatar
    Join Date
    May 2011
    Location
    La Vernia, Texas, United States
    Posts
    4

    Default

    Had this same issue, unplugged the MAF sensor and it fixed that problem. #5 plug is firing but the cylinder is not getting fuel, #6 sometimes gets fuel, I am very frustrated!
    To summarize, In thje end, we're all just a lil F***ed Up.
    Totally Customized 1997 GMC Jimmy SLS 4-door HHR Edition.
    All Customized by Yours Truely.
    Ride GM or DON'T Ride at all!

  10. #10

    Default

    #5 plug is firing but the cylinder is not getting fuel, #6 sometimes gets fuel, I am very frustrated!
    Assuming this is on a '97, I'd start by checking the fuel pressure and then checking the injectors. Sounds like something is preventing the 5 & 6 injectors from firing properly.
    '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

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