Mercury F2AZ-9B989-A Potentiometer - Engine Throttle

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Start by relieving fuel pressure, disconnecting the battery cable, and removing the air intake plenum assembly on 5.0L engines or the air intake assembly on 4.6L engines. Use a special spring lock coupling tool to disconnect the fuel feed and return lines from the fuel rail assembly. Remove the four fuel rail assembly retaining bolts and carefully disengage the fuel rail from the fuel injectors. The installation process is the reverse of removal.

When working with the PCM (also known as the EEC-V module) or associated harness, exercise caution to avoid direct contact with the electrical connector terminals, as static electricity can damage delicate electronic components inside the PCM. It is recommended to wear a static discharging wrist strap and avoid working on electronics when relative humidity is under 25 percent. General EEC-IV power relay and ground checks are essential to prevent confusion and inaccurate diagnosis. The EEC relay and associated circuits provide battery power (VPWR) to fuel injection and electric fuel pump-related components requiring 10.5 volts or greater. The PCM (EEC-IV) reduces the input voltage to four-to-six volts for output to sensors requiring a specific reference voltage (VREF). For fuel delivery component and circuit checks, verify proper electrical operation of the fuel pump relay, inertia switch, fuel pump(s), fuel injectors, and fuel tank selector switch on dual tank models. Information sensors and output actuators include the engine coolant temperature sensor, which is a thermistor varying its voltage output based on temperature changes. Resistance values change with temperature, and failure in the coolant sensor circuit may set a diagnostic code. To check the sensor, measure its resistance values when cold and at operating temperature, ensuring correct values. Verify the signal voltage to the sensor from the PCM, which should be approximately 5.0 volts. Before installing a new sensor, wrap the threads with Teflon sealing tape. The Manifold Absolute Pressure (MAP) sensor monitors intake manifold pressure changes and converts them into a voltage output. There are voltage-varying and frequency-varying types of MAP sensors. A failure in the MAP sensor circuit may set a diagnostic code. Check the reference voltage to the MAP sensor and back probe the harness to determine the sensor type. Test the sensor response with a tachometer and a handheld vacuum pump, ensuring a smooth transition between readings. Replace the MAP sensor if test results are incorrect. The heated oxygen sensor (HO2S) monitors the oxygen content of the exhaust gas stream, producing a voltage output that varies with the air-to-fuel ratio. Diagnostic codes indicate problems in the oxygen sensor system. Check the sensor's steady signal voltage between 0.35 and 0.55 volts at normal operating temperature. The sensor's proper operation depends on electrical connections, outside air supply, operating temperature, and the use of unleaded fuel. Take special care during sensor service to avoid damage. When replacing the oxygen sensor, use caution due to the sensor's location in the exhaust manifold or pipe. Start and run the engine briefly before removal to facilitate loosening. Disconnect the battery, raise the vehicle, disconnect the electrical connector, unscrew the sensor, apply anti-seize compound to the threads, install the new sensor, and reconnect the electrical connector. The Throttle Position Sensor (TPS) is located on the throttle body and monitors throttle valve angle, affecting fuel delivery. Problems in the TPS or circuit may set a diagnostic code. To check the TPS, measure the signal voltage at idle and full-open throttle positions. Verify the TPS reference voltage and resistance of the potentiometer within the TPS. Adjust the TPS if necessary. The Intake Manifold Temperature Sensor, also known as the Air Charge Temperature (ACT) sensor, is located in the intake manifold and acts as a resistor changing value with air temperature. Problems with the IAT sensor may set a diagnostic code. Check the reference voltage and measure resistance across the sensor terminals at different temperatures. Power steering pressure switch issues may cause timing to retard at idle or engine stalling under heavy power steering use. A pressure switch that fails to open or close may impact engine performance. Check for battery voltage to the power steering pressure switch and continuity to brake light bulbs. The Brake On/Off (BOO) switch indicates brake application to the PCM. Issues with the BOO switch or circuit may affect idle quality. Check for battery voltage to the BOO switch and continuity to brake light bulbs. The EGR Valve Position (EVP) sensor attached to the EGR valve produces a signal indicating the EGR valve's position. Check for reference voltage and resistance of the EVP sensor. Apply vacuum and check resistance change. Replace the EVP sensor if necessary. The Knock Sensor (KS) detects engine detonation, sending a voltage signal to the PCM to retard spark timing. Check for reference voltage to the knock sensor and simulate operating conditions to observe timing response. Replace the knock sensor if it does not respond. The Idle Air Control (IAC) or Bypass Air Idle Speed Control (BPA-ISC) solenoid controls idle speed by regulating air bypassing the throttle body. Check for the PCM signal voltage, inspect the pintle for carbon deposits, and check the resistance of the solenoid. Clean the IAC valve housing and install a new O-ring during replacement. The Mass Airflow (MAF) sensor measures air entering the engine using a hot wire sensing element. Check for power to the MAF sensor and voltage signals at idle and increased engine speed. Disconnect the MAF sensor and check for resistance. Replace the MAF sensor if necessary. The Manual Lever Position (MLP) sensor on the transmission indicates the gear position to the PCM. Check for power to each signal wire and adjust the switch if necessary. Further diagnostics require specialized equipment.

To remove the air intake plenum (upper intake manifold) and throttle body on a 5.0L engine, first disconnect the negative battery cable, then unplug electrical connectors at the air bypass valve, throttle position sensor, and EGR position sensor. Detach the accelerator cable and transmission linkage from the throttle body assembly, remove the accelerator cable/throttle valve (TV) cable bracket from the intake manifold, and label and detach vacuum lines from the upper intake manifold vacuum tree, EGR valve, and fuel pressure regulator. Disconnect the PCV system and, if present, the canister purge line and EGR spacer coolant lines (draining the coolant if needed). Remove the six upper intake manifold retaining bolts and the upper intake manifold and throttle body as an assembly from the lower intake manifold. During installation, ensure the gasket is in place, position the new gasket(s) onto the lower intake mounting face, and secure the air intake plenum and throttle body assembly with the six upper intake manifold retaining bolts, tightening them to the specified torque. For the throttle body on 5.0L and 4.6L engines, begin by detaching the negative battery cable and the throttle position sensor and throttle air bypass valve electrical connectors. Disconnect the accelerator cable and Throttle Valve (TV) cable (if equipped), as well as the PCV vent closure hose (if present). Remove the four throttle body mounting nuts and, on 5.0L engines, carefully separate the throttle body from the EGR spacer, discarding the gasket for 5.0L engines. During installation, ensure the gasket mating surfaces are clean and free of damage, and tighten the throttle body mounting nuts to the specified torque. For the fuel rail assembly, relieve fuel pressure, disconnect the battery cable, and remove the air intake plenum assembly on 5.0L engines or the air intake assembly on 4.6L engines. Use a special spring lock coupling tool to disconnect the fuel feed and return lines from the fuel rail assembly, then remove the four fuel rail assembly retaining bolts (two on each side) and carefully disengage the fuel rail from the fuel injectors. Installation is the reverse of removal. For the fuel pressure regulator, relieve fuel system pressure, disconnect the battery cable, and detach the vacuum hose from the regulator. On 4.6L engines, remove the fuel rail bolts to access the regulator mounting bolts, then remove the regulator, replace its O-rings, and lubricate them with oil before installation. For fuel injectors, relieve fuel pressure, remove the air intake plenum assembly on 5.0L engines or the air intake assembly on 4.6L engines, and remove the fuel rail assembly. Carefully detach the electrical connectors from the injectors, remove the injectors by pulling up while gently rocking them from side-to-side, and inspect and replace injector O-rings and other components as needed. Lubricate new O-rings with oil before installation and twist to install the injectors. The remainder of the installation is the reverse of removal.

You should check terminal connectors for attachment, verify power, and adjust if necessary. Diagnostics require special tools.