1991 1999 ford explorer chilton User Manual

							Exploded view of the EGR system and related components for the 3.0L engine
Click to enlarge
HOW TO USE THIS BOOK
COMPONENT TESTING 527 
						

							Exploded view of the EGR system and related components for the 4.0L engine
Click to enlarge
System Integrity Inspection
Check the EGR system hoses and connections for looseness, pinching, leaks, splitting, blockage, etc. Ensure
that the EGR valve mounting bolts are not loose, or that the flange gasket is not damaged. If the system
appears to be in good shape, proceed to the EGR vacuum test, otherwise repair the damaged components.
EGR System Vacuum Test
The EVR solenoid has a constant internal leak; this is normal. There may be a small vacuum signal,
however, it should be less than 1.0 in. Hg (3.4 kPa) of vacuum.
Start the engine and allow it to run until normal operating temperature is reached. With the engine running at
idle, detach the vacuum supply hose from the EGR valve and install a vacuum gauge to the hose. The vacuum
reading should be less than 1.0 in. Hg (3.4 kPa) of vacuum. If the vacuum is greater than that specified, the
problem may lie with the EVR solenoid.
EVR Solenoid Test Remove the EVR solenoid.
1. 
Attempt to lightly blow air into the EVR solenoid. If air blows through the solenoid, replace the solenoid with a new one.
1. 
If air does not pass freely through the solenoid, continue with the test.
2. 
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528 COMPONENT TESTING 
						

							Apply battery voltage (approximately 1 volts) and a ground to the EVR solenoid electrical terminals.
Attempt to lightly blow air, once again, through the solenoid. If air does not pass through the solenoid, replace the solenoid with a new one.
1. 
If air does not flow through the solenoid, the solenoid is OK.
2. 
3. 
EGR Valve Function Test Install a tachometer on the engine, following the manufacturers instructions.
1. 
Detach the engine wiring harness connector from the Idle Air Control (IAC) solenoid.
2. 
Disconnect and plug the vacuum supply hose from the EGR valve.
3. 
Start the engine, then apply the parking brake, block the rear wheels and position the transmission in
Neutral.
4. 
Observe and note the idle speed.
5. 
If the engine will not idle with the IAC solenoid disconnected, provide an air bypass to the engine by
slightly opening the throttle plate or by creating an intake vacuum leak. Do not allow the idle speed to
exceed typical idle rpm.
Some EGR valves may be tested using a vacuum pump by watching for diaphragm movement
Using a hand-held vacuum pump, slowly apply 5-10 in. Hg (17-34 kPa) of vacuum to the EGR
valve nipple. If the idle speed drops more than 100 rpm with the vacuum applied and returns to normal
after the vacuum is removed, the EGR valve is OK.
1. 
If the idle speed does not drop more than 100 rpm with the vacuum applied and return to
normal after the vacuum is removed, inspect the EGR valve for a blockage; clean it if a
blockage is found. Replace the EGR valve if no blockage is found, or if cleaning the valve
does not remedy the malfunction.
2. 
6. 
REMOVAL & INSTALLATION
PFE/DPFE Sensor
This component is found on all engines, and is also referred to as the backpressure transducer. Disconnect the negative battery cable.
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COMPONENT TESTING 529 
						

							Detach and label the wiring harness connector from the PFE/DPFE sensor.
2. 
Disconnect all of the hoses from the sensor.
3. 
Remove the mounting nuts, then separate the sensor from the mounting bracket.
4. 
If necessary, remove the EVR solenoid and the PFE/DPFE mounting bracket from the upper intake
manifold.
5. 
To install: If removed, install the EVR solenoid and mounting bracket onto the upper intake manifold.
6. 
If applicable, install the EGR tube heat shield.
7. 
Position the PFE/DPFE sensor on the mounting bracket, then install and tighten the mounting nuts
until snug.
8. 
Attach all necessary hoses and wiring to the sensor.
9. 
Connect the negative battery cable.
10. 
EGR Vacuum Regulator (EVR) Solenoid
The EVR solenoid is mounted either on the same bracket as the PFE/DPFE sensor, attached to the
upper intake manifold, or near the EGR valve on its own bracket.
Disconnect the negative battery cable.
1. 
Label and detach the wiring harness connector from the EVR solenoid.
2. 
Detach the main emission vacuum control connector from the solenoid.
3. 
Remove the retaining nuts, then separate the solenoid from the mounting bracket.
4. 
To install: Position the solenoid on its mounting bracket and install the retaining nuts.
5. 
Attach the main emission vacuum control connector and the wiring harness connector to the EVR
solenoid.
6. 
Connect the negative battery cable.
7. 
EGR Valve Disconnect the negative battery cable.
1. 
If necessary, remove the air inlet tube from the throttle body and air cleaner housing.
2. 
Label and detach all vacuum hoses from the EGR valve.
3. 
Label and detach any electrical wiring harness connectors from the EGR valve.
4. 
Disconnect the EGR valve-to-exhaust manifold tube from the EGR valve.
5. 
Remove the EGR valve mounting fasteners, then separate the valve from the upper intake manifold.
6. 
Remove and discard the old EGR valve gasket, and clean the gasket mating surfaces on the valve and
the intake manifold.
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530 REMOVAL & INSTALLATION 
						

							Cutaway view of a base entry type EGR valve
Click to enlarge
Cutaway view of a side entry type EGR valve Click to enlarge
To install: HOW TO USE THIS BOOK
REMOVAL & INSTALLATION 531 
						

							Install the EGR valve, along with a new gasket, on the upper intake manifold, then install and tighten
the mounting bolts to 4-22 ft. lbs. (20-30 Nm) on 3.8L engines, or to 106-49 inch lbs. (1-18 Nm) on
5.0L engines.
8. 
Connect the EGR valve-to-exhaust manifold tube to the valve, then tighten the tube nut to 30 ft. lbs.
(41 Nm).
9. 
Connect all wiring or hoses to the EGR valve.
10. 
Install the air inlet tube.
11. 
Connect the negative battery cable.
12. 
Chilton® Automotive Information Systems. © 2004 Thomson Delmar Learning. HOW TO USE THIS BOOK
532 REMOVAL & INSTALLATION 
						

							
ELECTRONIC ENGINE CONTROLS
Electronic Engine Control (EEC)
All Sequential Fuel Injection (SFI) systems use the EEC system. The heart of the EEC system is a
micro-processor called the Powertrain Control Module (PCM). The PCM receives data from a number of
sensors and other electronic components (switches, relay, etc.). Based on information received and
information programmed in the PCMs memory, it generates output signals to control various relay, solenoids
and other actuators. The PCM in the EEC system has calibration modules located inside the assembly that
contain calibration specifications for optimizing emissions, fuel economy and drive ability. The calibration
module is called a PROM.
The following are the electronic engine controls used by 1991-99 Ranger/Explorer and Mountaineers: Powertrain Control Module (PCM)
· 
Throttle Position (TP) sensor
· 
Mass Air Flow (MAF) sensor
· 
Intake Air Temperature (IAT) sensor
· 
Idle Air Control (IAC) valve
· 
Engine Coolant Temperature (ECT) sensor
· 
Heated Oxygen Sensor (HO2S)
· 
Camshaft Position (CMP) sensor
· 
Knock Sensor (KS)
· 
Vehicle Speed Sensor (VSS)
· 
Crankshaft Position (CKP) sensor
· 
The MAF sensor (a potentiometer) senses the position of the airflow in the engines air induction system and
generates a voltage signal that varies with the amount of air drawn into the engine. The IAT sensor (a sensor
in the area of the MAF sensor) measures the temperature of the incoming air and transmits a corresponding
electrical signal. Another temperature sensor (the ECT sensor) inserted in the engine coolant tells if the engine
is cold or warmed up. The TP sensor, a switch that senses throttle plate position, produces electrical signals
that tell the PCM when the throttle is closed or wide open. A special probe (the HO2S) in the exhaust
manifold measures the amount of oxygen in the exhaust gas, which is in indication of combustion efficiency,
and sends a signal to the PCM. The sixth signal, camshaft position information, is transmitted by the CMP
sensor, installed in place of the distributor (engines with distributorless ignition), or integral with the
distributor.
The EEC microcomputer circuit processes the input signals and produces output control signals to the fuel
injectors to regulate fuel discharged to the injectors. It also adjusts ignition spark timing to provide the best
balance between driveability and economy, and controls the IAC valve to maintain the proper idle speed.
Because of the complicated nature of the Ford system, special tools and procedures are necessary for
testing and troubleshooting.
Powertrain Control Module (PCM)
OPERATION
The Powertrain Control Module (PCM) performs many functions on your car. The module accepts
information from various engine sensors and computes the required fuel flow rate necessary to maintain the
ELECTRONIC ENGINE CONTROLS 533 
						

							
correct amount of air/fuel ratio throughout the entire engine operational range.
Based on the information that is received and programmed into the PCMs memory, the PCM generates output
signals to control relays, actuators and solenoids. The PCM also sends out a command to the fuel injectors
that meters the appropriate quantity of fuel. The module automatically senses and compensates for any
changes in altitude when driving your vehicle.
REMOVAL & INSTALLATION
Typical PCM module
491-92 Models
Disconnect the negative battery cable.
1. 
Remove the inside, lower cowl trim panel from the passengers side of the vehicle to expose the PCM.
2. 
Disengage the wiring harness connector from the PCM by loosening the connector retaining bolt, then
pulling the connector from the module.
3. 
Remove the PCM from the bracket by pulling the unit downward.
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							View of the right-hand kick panel PCM mounting for 491-92 models
Click to enlarge
To install: Install the PCM in the mounting bracket.
5. 
Attach the wiring harness connector to the module, then tighten the connector retaining bolt.
6. 
Install the right cowl trim panel.
7. 
Connect the negative battery cable.
8. 
493-99 Models
The module is mounted under the hood on the firewall. On 493-94 models, it is mounted low on the firewall,
near the left-hand fender (drivers side). On 495-99 models, it is mounted high on the firewall offset to the
right-hand side of center. HOW TO USE THIS BOOK
REMOVAL & INSTALLATION 535 
						

							Exploded view of the firewall PCM mounting for 493-94 models
Click to enlarge
Exploded view of the firewall PCM mounting for 495-99 models Click to enlarge
Disconnect the negative battery cable.
1. 
Disengage the wiring harness connector from the PCM by loosening the connector retaining bolt, then
pulling the connector from the module.
2. 
Remove the two nuts and the PCM cover.
3. 
Remove the PCM from the bracket by pulling the unit outward.
4. 
To install: Install the PCM in the mounting bracket.
5. 
Install the PCM cover and tighten the two nuts.
6. 
Attach the wiring harness connector to the module, then tighten the connector retaining bolt.
7. 
Connect the negative battery cable.
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536 REMOVAL & INSTALLATION