nissan pickup still not running right

Discussion in 'Automotive / Motorcycle Chat' started by country_boy, May 23, 2009.

  1. country_boy

    country_boy TGT Addict

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    got a 93' nissan hardbody 4 cylinder and once it gets to operating temp. it wont idle right. It drives fine on the highway. Ive changed the plugs, wires, cap, rotor twice in the past 2 months. The weird thing is, it isnt throwing a engine light. Any ideas? Vacuum lines all seem to be in good condition.
     


  2. M. Sage

    M. Sage TGT Addict

    Jan 21, 2009
    San Antonio
    What exactly is it doing? "Won't idle right" how?

    Misfire? Rough idle? Hunting idle? Idle low? Idle high? Stalls?
     
  3. country_boy

    country_boy TGT Addict

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    it sounds like it wants to die, then the idle goes back up for a little bit, then lower. Repeats.
     
  4. MadMo44Mag

    MadMo44Mag TGT Addict

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    Ft.Worth
    C-boy need some info to help
    Is the a Frontier?
    2x4 or 4x4?
    Auto or Std?

    It sounds like a TPS - Throttle Position Sensor

    Also any SES on? Service Engine Soon light

    More info
    "
    The throttle position sensor responds to the accelerator pedal movement. This sensor is a type of potentiometer which transforms the throttle position into output voltage, and emits the voltage signal to the ECM. In addition, the sensor detects the opening and closing speed of the throttle valve and feeds the voltage signal to the ECM.

    Idle position of the throttle valve is determined by the ECM receiving the signal from the throttle position sensor. This sensor controls engine operation such as fuel cut."
     
  5. country_boy

    country_boy TGT Addict

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    this is before the Frontier. This is a small pickup aka the hardbody. 93' d21
    2wd. auto transmission
    No check engine light is on. It is fuel injected(mpi)

    I was thinking it was the tps. However, I think a trip next month to Lambs is a good idea just to see what else might need replacing.
     
  6. MadMo44Mag

    MadMo44Mag TGT Addict

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    This is a likely cause.

    Classification: EF&EC94-O16
    Section: Engine Control System
    Models: Trucks (D21) with KA24E Engine
    Reference: TECHNICAL BULLETIN NTB94-106
    Date: November 22, 1994
    TRUCK(D21) ENGINE IDLE FLUCTUATION
    APPLIED MODEL:
    Truck(D21) with KA24E Engine SERVICE INFORMATION
    [​IMG]
    Some Trucks may exhibit a surge or an intermittent idle fluctuation. The incident may be difficult to diagnose, causing several repair attempts to be made. Such incidents may be caused by a poor electrical connection at a splice joint where the ground wire (B/G) from the E.C.M. meets three other wires from the Engine Coolant Temperature Sensor, Exhaust Gas Recirculation Temperature Sensor and the Throttle Position Switch. If the splice joint connection is poor, the ground for these sensors is intermittently interrupted, causing improper E.C.M. input readings. The incident may be induced or alleviated by moving the engine/injector harness by hand as shown (Figure 1).
    SERVICE PROCEDURE
    [​IMG]
    1. Remove air cleaner assembly and detach engine harness from engine (section between valve cover and throttle body). (Figure 2) 2. Remove the harness covering (plastic shield/electrical tape) and locate the splice connection. A single ground wire (B/G) is connected to three other wires (also, B/G) with a pressed metal connector. [​IMG]
    To ensure a positive connection at this splice, solder the metal connector to the wires to form a permanent connection (Figure 3).
    3. Wrap soldered splice with heat shrink tape to ensure a waterproof seal. Reinstall plastic shield and wrap with 3M Electrical Tape (3M P/N 88) or equivalent. 4. Reattach harness to engine and replace air cleaner assembly. 5. Test drive vehicle to ensure that incident is resolved. [​IMG]
     
  7. MadMo44Mag

    MadMo44Mag TGT Addict

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    Also -

    Throttle Position Sensor (TPS) Operating Characteristics [​IMG]

    PURPOSE
    To provide the ECM with a voltage signal that corresponds to the opening angle of the throttle.

    LOCATION
    Mounted to the side of the throttle housing.

    OPERATION
    The Throttle Position Sensor has both a linear potentiometer (sensor) and Idle/Wide Open Throttle (WOT) switches.

    Throttle Sensor:
    The sensor receives a 5 VDC reference signal from the ECM. At idle, the sensor will output approx. 0.4 VDC to the ECM and upwards of 4.5 VDC at wide open throttle. The ECM uses this voltage signal to calculate throttle opening angle and the speed at which the throttle was opened.

    Throttle Switches:
    The Throttle Switches (Idle and WOT) are NOT used by the ECM to manage the ECCS system. The switches are used by ECM for self-diagnostic purposes only.

    Testing

    Fig. 153 Throttle Sensor Inspection [​IMG]


    1. Disconnect throttle sensor connector.
    2. Using an ohm meter, check resistance across terminals e and f. Resistance value should change smoothly, without any glitches, from approximately 1 to approximately 9 ohms as the throttle is moved from idle to WOT. Replace sensor if it fails the above test.

    REMOVAL


    1. Turn the ignition key off.
    2. Remove the intake air duct from the throttle chamber.
    3. Disconnect the idle switch and throttle sensor connectors.
    4. Remove the 2 bolts securing the unit to the throttle chamber and remove the unit.
    Throttle Sensor [​IMG]

    INSTALLATION AND ADJUSTMENT


    1. Install the unit to the throttle shaft, aligning the flat area on the shaft with the flat area on the unit.
    2. Install the screws and tighten slightly.
    3. Reconnect the throttle sensor and idle switch connectors.
    4. Install the intake air duct.
    5. Start the engine and warm to operating temperature.
    6. Using a volt meter, check the output voltage between terminals as shown.

      1. If the voltage is between 0.4 - 0.6 vdc at idle, the sensor is adjusted properly.
      2. If the voltage is not between 0.4 - 0.6 vdc at idle, proceed to step 3.

    1. Loosen the throttle sensor securing screws (2).
    2. Rotate the sensor until 0.4 - 0.6 vdc is measured between the terminals at idle.
    3. Tighten the screws and recheck the voltage.
     
  8. country_boy

    country_boy TGT Addict

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    I appreciate it, I will show this to my uncle, Im not good with electrical and or computerized sensors on vehicles. That and I dont own a soldering iron yet.
     
  9. M. Sage

    M. Sage TGT Addict

    Jan 21, 2009
    San Antonio
    Doubtful that it's the TPS. The bad splice connection is more likely, but I'd try cleaning the throttle body with carb cleaner first.

    Hold the throttle wide open; note where the throttle plate sits close to the bore, spray the bore with cleaner and wipe the area where the throttle plate rests near the bore with a rag. Give it another spray to get the rest of the gunk off (may have to repeat the second step a couple of times if it's really bad), then start the truck.

    It'll be hard to start since it's flooded. You can either let it sit overnight and try in the morning, or you can hold the accelerator to the floor to turn the fuel injectors off. Once it starts it'll take maybe 10 seconds to clear the cleaner out of the engine.

    Probably 90% of the idle problems (not counting misfires) I run into at work are fixed with a throttle cleaning.
     
  10. country_boy

    country_boy TGT Addict

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    Cant be the throttle body, I ran three cans of b-12 chemtool and cleaned it.
    I also dont run 87 octane, I run 89 octane with seafoam so everything stays clean,
    I bet it is the splice.
     

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