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Question with my 1991 K1500

Discussion in 'Truck & Equipment Repair' started by velocityllc, Nov 16, 2010.

  1. velocityllc

    velocityllc Junior Member
    Messages: 2

    Its a 350 engine just changed spark plugs and wiring as well as alternator and battery and starter. My problem arises after truck is warm it has a rough idle thats very inconsistant (meaning only sometimes it does this.) now seems that during deceleration and at low speeds lights will dim and can completly shut the engine down in drive or neutral. starts up one key turn after no problem and seems to happen more when turning due to power steering i would assume helps bog the engine. anyone have this type of problem? if you need more info just ask i will try my best to answer all the questions i appreciate the help.
  2. hydro_37

    hydro_37 PlowSite Veteran
    from iowa
    Messages: 3,790

    check your ground wires and connections
  3. velocityllc

    velocityllc Junior Member
    Messages: 2

    I did that they seem clean another problem that may or not be relaited to this but when the throtle is pushed down half an inch for daily driving and staying under speedlimit the truck with start to jump back and forth like a rocking motion only at that throtle not under acceleration or at 50+mph speeds will it do this. Im stumped
  4. jlord85

    jlord85 Junior Member
    from Chicago
    Messages: 9

    Have someone put a fuel pressure gauge on it and test your fuel pump. When mine went, it was doing the same thing. Put the fuel pump in yourself if you can. I paid 1500 mostly for labor because I didnt have the time and rust is a pain.
  5. cssjim

    cssjim Junior Member
    from CT
    Messages: 26

    A faulty throttle position switch (TPS) can result in a number of poor running problems. Because they can result in such a large number of problems, faulty switches often go undiagnosed. The other thing that makes TPS problems difficult to diagnose is that they quite often only appear when the engine is warmed up (throttle position switch warmed up).

    The following lists some of the symptoms that MAY indicate a problem with the throttle position switch:

    * Poor idle - particularly a high idle condition
    * Engine cuts out to an idle condition during acceleration
    * Poor power at various RPMs (various throttle positions)
    * Surging idle
    * Misfire
    * Stumble during acceleration
    * Intermittent boost problems (turbocharged cars)


    * Multimeter
    * Test leads
    * Phillips screwdriver



    On 1985.5 and newer cars, the DME control unit is located behind the kick panel in the passenger's footwell. For pre-1985.5 cars, the DME is located under the dash on the driver's side.

    For 8V Normally Aspirated cars:

    1. Disconnect the electrical connector for the DME.

    2. Connect an ohmmeter between terminal 2 on the DME wiring harness plug and ground. This will test the idle speed contact. With the throttle closed, the ohmmeter should read zero (0) ohms. With the throttle open, the ohmmeter should read infinite (∞). The switch in resistance must occur as soon as the throttle starts to open (approximately 1°).
    3. Connect the ohmmeter between terminal 3 on the DME wiring harness plug and ground. This will test the wide open throttle (WOT) contact. With the throttle closed, the ohmmeter should read infinite (∞). With the throttle wide open the ohmmeter should read zero (0) ohms. The switch in resistance should occur just before the throttle reaches full open.
    4. If reading at the DME plug are unsatisfactory, the test should be repeated at the switch. This will require removing the throttle body from the car. The ohmmeter should be connected between the center terminal on the switch (ground) and each of the outer terminals (2 and 3) and resistance values checked as described above.