1991 1999 ford explorer chilton User Manual

							
The sensor utilizes a hot wire sensing element to measure the amount of air entering the engine. The sensor
does this by sending a signal, generated by the sensor when the incoming air cools the hot wire down, to the
PCM. The signal is used by the PCM to calculate the injector pulse width, which controls the air/fuel ratio in
the engine. The sensor and plastic housing are integral and must be replaced if found to be defective.
The Mass Air Flow (MAF) sensor is mounted to the air cleaner housing
The sensing element (hot wire) is a1 thin platinum wire wound on a ceramic bobbin and coated with glass.
This hot wire is maintained at 392°F (200°C) above the ambient temperature as measured by a constant cold
wire.
TESTING With the engine running at idle, use a DVOM to verify there is at least 10.5 volts between terminals
Aand Bof the MAF sensor connector. This indicates the power input to the sensor is correct. Then,
measure the voltage between MAF sensor connector terminals Cand D. If the reading is
approximately 0.34-1.96 volts, the sensor is functioning properly.
1.  HOW TO USE THIS BOOK
OPERATION 547 
						

							MAF sensor wire harness connections
Click to enlarge
REMOVAL & INSTALLATION CAUTION
The mass air flow sensor hot wire sensing element and housing are calibrated as a unit and must be serviced
as a complete assembly. Do not damage the sensing element or possible failure of the sensor may occur.
Disconnect the negative battery cable.
1.  HOW TO USE THIS BOOK
548 TESTING 
						

							To remove the MAF sensor, first disconnect the wire harness plug ...
... then remove the air cleaner-to-throttle body air tube
Disengage the wiring harness connector from the MAF sensor, and if necessary, the IAT sensor.
2. 
Loosen the engine air cleaner outlet tube clamps, then remove the tube from the engine.
3. 
Remove the MAF sensor from the air cleaner assembly by disengaging the retaining clips.
4. 
Remove the four MAF sensor attaching screws ...HOW TO USE THIS BOOK
REMOVAL & INSTALLATION 549 
						

							... then remove the sensor from the air cleaner housing
To install:
Install the MAF sensor to the air cleaner assembly and ensure that the retaining clips are fully
engaged.
5. 
Install the air cleaner outlet tube, then tighten the outlet tube clamps until snug.
6. 
Attach the engine wiring harness connectors to the IAT and MAF sensors.
7. 
Connect the negative battery cable.
8. 
Throttle Position (TP) Sensor
OPERATION
The Throttle Position (TP) sensor is a potentiometer that provides a signal to the PCM that is directly
proportional to the throttle plate position. The TP sensor is mounted on the side of the throttle body and is
connected to the throttle plate shaft. The TP sensor monitors throttle plate movement and position, and
transmits an appropriate electrical signal to the PCM. These signals are used by the PCM to adjust the air/fuel
mixture, spark timing and EGR operation according to engine load at idle, part throttle, or full throttle. The
TPS is not adjustable. HOW TO USE THIS BOOK
550 Throttle Position (TP) Sensor 
						

							Typical Throttle Position (TP) sensor mounting on the throttle body
TESTING Disconnect the negative battery cable.
1. 
Disengage the wiring harness connector from the TP sensor.
2. 
Using a Digital Volt-Ohmmeter (DVOM) set on ohmmeter function, probe the terminals, which
correspond to the Brown/White and the Gray/White connector wires, on the TP sensor. Do not
measure the wiring harness connector terminals, rather the terminals on the sensor itself.
3. 
Slowly rotate the throttle shaft and monitor the ohmmeter for a continuous, steady change in
resistance. Any sudden jumps, or irregularities (such as jumping back and forth) in resistance
indicates a malfunctioning sensor.
4. 
Reconnect the negative battery cable.
5. 
Turn the DVOM to the voltmeter setting.
6. 
WARNING
Ensuring the DVOM is on the voltmeter function is vitally important, because if you measure circuit
resistance (ohmmeter function) with the battery cable connected, your DVOM will be destroyed.
Detach the wiring harness connector from the PCM (located behind the lower right-hand kick panel
in the passengers compartment), then install a break-out box between the wiring harness connector
and the PCM connector.
7. 
Turn the ignition switch ONand using the DVOM on voltmeter function, measure the voltage
between terminals 89 and 90 of the breakout box. The specification is 0.9 volts.
8. 
If the voltage is outside the standard value or if it does not change smoothly, inspect the circuit wiring
and/or replace the TP sensor.
9.  HOW TO USE THIS BOOK
OPERATION 551 
						

							TP sensor wire harness connections
REMOVAL & INSTALLATION Disconnect the negative battery cable.
1. 
To remove the TP sensor, first disconnect the wire harness plug from the sensor
If the mounting holes of the sensor are slotted, mark its position. Note: factory sensors are not slotted
Disengage the wiring harness connector from the TP sensor.
2. 
Remove the two TP sensor mounting screws, then pull the TP sensor out of the throttle body housing.
3.  HOW TO USE THIS BOOK
552 TESTING 
						

							Remove the two attaching screws ...
... then remove the sensor from the throttle body by lifting straight up to disengage the throttle blade (arrow)
To install:
Position the TP sensor against the throttle body housing, ensuring that the mounting screw holes are
aligned. When positioning the TP sensor against the throttle body, slide the sensor straight onto the
housing.
4. 
Install and tighten the sensor mounting screws until snug.
5. 
Attach the wiring harness connector to the sensor, then connect the negative battery cable.
6. 
The TP sensor is not adjustable.
Camshaft Position (CMP) Sensor
OPERATION
The CMP sensor provides the camshaft position information, called the CMP signal, which is used by the
Powertrain Control Module (PCM) for fuel synchronization. HOW TO USE THIS BOOK
REMOVAL & INSTALLATION 553 
						

							
1991-93 2.3L and 1991-95 4.0L (VIN X) engines did not use CMP sensors.
1994 2.3L California only and 1995-99 2.3L and 2.5L engines utilize CMP sensors. The 1994 CMP is located
on the oil pump drive assembly, on the left-hand lower side of the engine block. 1995-99 models CMP
sensor is located and triggered by the auxiliary shaft drive sprocket.
On the 1991-94 2.9L and 3.0L engine, the distributor stator is the Camshaft Position (CMP) sensor, and it is a
Hall effect magnetic switch. On the 1995-99 3.0L engine, the CMP is mounted on the oil pump drive
assembly, located towards the rear of the block. it is also a single hall effect magnetic switch and it is
activated by a single vane, and is driven by the camshaft.
Camshaft Position (CMP) sensor used on the 2.3L and 2.5L engine-except 1994 California Click to enlarge
HOW TO USE THIS BOOK
554 OPERATION 
						

							Oil pump drive mounted CMP sensor used on 3.0L, 4.0L and 5.0L engines and 1994 California
2.3L engines
On the 4.0L SOHC engine (VIN E), the Camshaft Position (CMP) sensor is a variable reluctance sensor,
which is triggered by the high-point mark on the left-hand camshaft. It is mounted to the valve cover.
The 4.0L and 5.0L engines use a separate CMP sensor mounted to the oil pump drive. The drive assembly is
located toward the rear of the engine on the 4.0L, and towards the front on the 5.0L engine.
TESTING
Three Wire Sensors With the ignition OFF, disconnect the CMP sensor. With the ignition ONand the engine OFF,
measure the voltage between sensor harness connector VPWRand PWR GNDterminals (refer to the
accompanying illustration). If the reading is greater than 10.5 volts, the power circuit to the sensor is
okay.
1. 
With the ignition OFF, install break-out box between the CMP sensor and the PCM. Using a Digital
Volt-Ohmmeter (DVOM) set to the voltage function (scale set to monitor less than 5 volts), measure
voltage between break-out box terminals 24and 40with the engine running at varying RPM. If the
voltage reading varies more than 0.1 volt, the sensor is okay.
2.  HOW TO USE THIS BOOK
TESTING 555 
						

							CMP sensor wire harness connections for the 3-wire sensor
Click to enlarge
Two Wire Sensors With the ignition OFF, install a break-out box between the CMP sensor and PCM.
1. 
Using a Digital Volt-Ohmmeter (DVOM) set to the voltage function (scale set to monitor less than 5
volts), measure the voltage between break-out box terminals 24and 46with the engine running at
varying RPM. If the voltage reading varies more than 0.1 volt AC, the sensor is okay.
2. 
CMP sensor wire harness connections for the 2-wire sensor Click to enlarge
REMOVAL & INSTALLATION
1995-97 2.3L and 1998-99 2.5L Engines
According to the manufacturer, the A/C system, if equipped, must be discharged for this procedure.
Have your A/C system refrigerant reclaimed by an MVAC certified repair shop. However, there may
be enough flex or slack in the A/C lines to allow you to support the compressor off to the side without
disconnecting the lines.
Disconnect the negative battery cable.
1. 
Remove the accessory drive belt.
2. 
Remove the four bolts securing the A/C compressor to the mounting bracket and set aside.
3. 
Remove the three compressor/power steering bracket retaining bolts.
4. 
Pull the bracket, with the power steering pump attached, away from the engine and position it aside.
5. 
Disconnect the engine control sensor wiring from the camshaft position sensor.
6. 
Remove the two CMP mounting bolts and then pull the sensor from the oil pump.
7. 
To install: Install the CMP sensor to the oil pump and tighten the two mounting screws to 45-61 inch lbs. (5-7
Nm).
8.  HOW TO USE THIS BOOK
556 TESTING