1991 1999 ford explorer chilton User Manual

View of the TFI-IV ignition system components
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SYSTEM OPERATION
The CMP sensor, housed inside the distributor, responds to a rotating metallic shutter mounted on the
distributor shaft. This rotating shutter produces a digital Profile Ignition Pick-up (PIP) signal, which is used
by the PCM and ICM to provide base timing information, determine engine speed (rpm) and crankshaft
position. The distributor shaft rotates at one-half crankshaft speed, therefore the shutter rotates once for every...

During the CCD mode, both edges of the SPOUT signal are utilized. The leading edge of the SPOUT signal is
used by the ICM in the same manner as during the push start mode. The falling edge of the signal is generated
to control the timing for turning the ignition coil on (the ICM no longer controls this function as during the
push start mode). During the CCD mode, the coil on time, or dwell, is entirely controlled by the PCM through
the SPOUT signal.
In the event that the SPOUT signal from the PCM is...

Secondary coil voltage test 1 chart-crank mode check
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RUN MODE
Fully apply the parking brake. Place the gear shift lever in Neutral (manual transmission) or Park
(automatic transmission).
1. 
Disconnect the Sterminal wire at the starter relay. Attach a remote starter switch.
2. 
Turn the ignition switch to theRUNposition.
3. 
Using the remote starter switch, crank the engine and check for spark.
4. 
Turn the ignition switchOFF.
5. 
If no spark occurred, the problem lies with the wiring...

Secondary coil voltage test 2 chart-run mode check
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HOW TO USE THIS BOOK
TEST PROCEDURES 173 

Wiring harness test 3 chart-voltage check
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HOW TO USE THIS BOOK
174 TEST PROCEDURES 

Distributor hall effect test 4 chart
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ICM Test Remove the ICM from the distributor or the front fender apron.
1. 
Measure the resistance between the ICM terminals as shown below: GND-PIP IN: should be greater than 500 ohms.
1. 
PIP PWR-PIP IN: should be less than 2,000 ohms.
2. 
PIP PWR-TFI PWR: should be less than 200 ohms.
3. 
GND-IGN GND: should be less than 2 ohms.
4. 
PIP IN-PIP: should be less than 200 ohms.
5. 
2. 
If any of these checks failed, replace the ICM with a new one.
3....

ICM module resistance test 5 chart
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ICM module test 6 chart Click to enlarge
System Test Disconnect the pin-in-line connector near the ICM.
1. 
Crank the engine
2. 
Turn the ignition switch OFF.
3. 
If a spark did occur, check the PIP and ignition ground wires for continuity. If okay, the problem is
not in the ignition system.
4. 
If no spark occurs, check the voltage at the positive (+) terminal of the ignition coil with the ignition
switch in RUN.
5. 
If the reading is not within...

Schematic of the TFI-IV ignition system
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Spark Timing Advance Test
Spark timing advance is controlled by the EEC system. This procedure checks the capability of the ignition
module to receive the spark timing command from the EEC module. The use of a volt/ohmmeter is required.
Turn the ignition switch OFF.
1. 
Disconnect the pin-in-line connector (SPOUT connector) near the TFI module.
2. 
Start the engine and measure the voltage, at idle, from the SPOUT connector to the distributor base....

Secondary coil wire test 7 chart
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Crank the engine and check for spark.
3. 
Turn the ignition switch OFF.
4. 
If a spark did occur, measure the resistance of the ignition coil wire, replace it if the resistance is
greater than 7000 ohms per foot. If the readings are within specification, replace the ignition coil.
5. 
If no spark occurs, the problem is not the coil.
6. 
Ignition Coil Supply Voltage Remove the/coil connector.
1. 
Attach the negative (-) lead from a Volt/ohmmeter to the...

Ignition coil supply voltage test 8 chart
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Ignition Coil Primary Resistance Test Turn the ignition switch off, then disconnect the ignition coil connector.
1. 
Check for dirt, corrosion or damage.
2. 
Ignition coil primary resistance test
Use an ohmmeter to measure the resistance from the positive (+) to negative (-) terminals of the
ignition coil.
3. 
If the reading is between 0.3-1.0 ohms the ignition coil is OK; continue on to the Ignition Coil
Secondary Resistance Test. If the reading...