1991 1999 ford explorer chilton User Manual

							Ignition coil secondary resistance test
REMOVAL & INSTALLATION Disconnect the negative battery cable.
1. 
Label and detach all wiring from the ignition coil.
2. 
Remove the ignition coil-to-bracket bolts, then remove the ignition coil.
3. 
If necessary, at this time the radio ignition interference capacitor can be removed from the ignition
coil.
4. 
To install: If necessary, install the radio interference capacitor onto the ignition coil. Tighten the mounting bolt
to 25-35 inch lbs. (2.8-4.0 Nm).
5. 
Position the ignition coil onto the mounting bracket, then install and tighten the mounting bolts to
25-35 inch lbs. (2.8-4.0 Nm).
6. 
Attach all wiring to the ignition coil, then connect the negative battery cable.
7. 
Ignition Control Module (ICM)
REMOVAL & INSTALLATION
Remote Mounted Module HOW TO USE THIS BOOK
180 REMOVAL & INSTALLATION 
						

							View of the remote mounted Ignition Control Module (ICM)
Click to enlarge
Disconnect the negative battery cable.
1. 
Label and detach all wiring from the ICM.
2. 
Remove the ICM/heatsink-to-fender apron bolts, then remove the ICM/heatsink.
3. 
If necessary, at this time the ICM can be removed from the heat sink.
4. 
To install: Apply an approximately  1
/32  in. (0.80mm) thick layer of silicone dielectric compound (D7AZ-19A331-A or equivalent) to the base
plate of the ICM. /
5. 
Install the ICM onto the heat sink. Tighten the mounting bolts to 15-35 inch lbs. (1.7-4.0 Nm).
6. 
Position the ICM onto the right-hand, front fender apron, then install and tighten the mounting bolts
to 90-120 inch lbs. (10-14 Nm).
7. 
Attach all wiring to the ICM, then connect the negative battery cable.
8. 
Distributor Mounted Module Disconnect the negative battery cable.
1. 
Remove the distributor assembly from the engine.
2. 
Place the distributor on the workbench and remove the module retaining screws. Pull the right side of
the module down the distributor mounting flange and back up to disengage the module terminal from
the connector in the distributor base. The module may be pulled toward the flange and away from the
distributor.
3. 
Do not attempt to lift the module from the mounting surface, except as explained above. The pins will
break at the distributor module connector.
To install: Coat the base plate of the TFI ignition module uniformly with  1
/32  inch of silicone dielectric
compound WA-10 or equivalent.
4. 
Position the module on the distributor base mounting flange. Carefully position the module toward the
distributor bowl and engage the three connector pins securely.
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REMOVAL & INSTALLATION 181 
						

							Install the retaining screws. Tighten to 15-35 inch lbs (1.7-4.0 Nm), starting with the upper right
screw.
6. 
Install the distributor into the engine. Install the cap and wires.
7. 
Reconnect the negative battery cable.
8. 
Recheck the initial timing. Adjust if necessary.
9. 
Distributor
REMOVAL & INSTALLATION
Exploded view of the distributor mounted ICM distributorClick to enlarge
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182 Distributor 
						

							Example of the remote mounted ICM distributor
Click to enlarge
Rotate the engine until the No. 1 piston is on Top Dead Center (TDC) of its compression stroke.
1. 
Disconnect the negative battery cable. Disconnect the vehicle wiring harness connector from the
distributor. Before removing the distributor cap, mark the position of the No. 1 wire tower on the cap
for reference.
2. 
Loosen the distributor cap hold-down screws and remove the cap. Matchmark the position of the
rotor to the distributor housing. Position the cap and wires out of the way.
3. 
Scribe a mark in the distributor body and the engine block to indicate the position of the distributor in
the engine.
4. 
Remove the distributor hold-down bolt and clamp.
5. 
Some engines may be equipped with a security-type distributor hold-down bolt. If this is the case, use
distributor wrench T82L-12270-A or equivalent, to remove the retaining bolt and clamp.
Remove the distributor assembly from the engine. Be sure not to rotate the engine while the
distributor is removed.
6. 
To install: Make sure that the engine is still with the No. 1 piston up on TDC of its compression stroke.
7. 
If the engine was disturbed while the distributor was removed, it will be necessary to remove the No. 1
spark plug and rotate the engine clockwise until the No. 1 piston is on the compression stroke. Align the
timing pointer with TDC on the crankshaft damper or flywheel, as required.
Check that the O-ring is installed and in good condition on the distributor body.
8. 
On all vehicles:
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REMOVAL & INSTALLATION 183 
						

							Rotate the distributor shaft so the rotor points toward the mark on the distributor housing
made previously.
1. 
Rotate the rotor slightly so the leading edge of the vane is centered in the vane switch state
assembly.
2. 
Rotate the distributor in the block to align the leading edge of the vane with the vane switch
stator assembly. Make certain the rotor is pointing to the No. 1 mark on the distributor base.
3. 
If the vane and vane switch stator cannot be aligned by rotating the distributor in the cylinder block,
remove the distributor enough to just disengage the distributor gear from the camshaft gear. Rotate the
rotor enough to engage the distributor gear on another tooth of the camshaft gear. Repeat Step 9 if
necessary.
Install the distributor hold-down clamp and bolt(s); tighten them slightly.
10. 
Attach the vehicle wiring harness connector to the distributor.
11. 
Install the cap and wires. Install the No. 1 spark plug, if removed.
12. 
Recheck the initial timing.
13. 
Tighten the hold-down clamp and recheck the timing. Adjust if necessary.
14. 
Camshaft Position (CMP) Sensor
For Camshaft Position (CMP) sensor procedures, please refer to Section 4 in this manual.
Chilton® Automotive Information Systems. © 2004 Thomson Delmar Learning. HOW TO USE THIS BOOK
184 Camshaft Position (CMP) Sensor 
						

							
DISTRIBUTORLESS IGNITION SYSTEM
General Information
The distributorless ignition system used by 1991-94 2.3L and 4.0L, and all 1995-99 engines is referred to as
the Electronic Ignition (EI) system. It eliminates the conventional distributor by utilizing multiple ignition
coils instead. The EI system consists of the following components:
Crankshaft Position (CKP) sensor
· 
Ignition Control Module (ICM) (EEC-IV systems only)
· 
Ignition coil(s)
· 
The spark angle portion of the Powertrain Control Module (PCM)
· 
Related wiring
· 
The function of the ICM was incorporated into the PCM beginning with the EEC-V system; otherwise
the newer system operates in the same manner.
SYSTEM OPERATION
The CKP sensor is a variable reluctance sensor, mounted near the crankshaft damper and pulley.
The crankshaft damper has a 36 minus 1 tooth wheel (data wheel) mounted on it. When this wheel rotates the
magnetic field (reluctance) of the CKP sensor changes in relationship with the passing of the teeth on the data
wheel. This change in the magnetic field is called the CKP signal.
The base ignition timing is set at 10 (plus or minus 2 degrees) degrees Before Top Dead Center (BTDC)
and is not adjustable.
EEC-IV Systems
The CKP signal is sent to the ICM, where it is used to create the Profile Ignition Pick-up (PIP) signal.
The one missing tooth on the data wheel creates one large space between two of the teeth. The ICM utilizes
this large space as a reference to help determine base ignition timing and engine speed (rpm), and to
synchronize the ignition coils for the proper spark timing sequence.
DISTRIBUTORLESS IGNITION SYSTEM 185 
						

							Common wiring schematic for an EEC-IV distributorless ignition system
Click to enlarge
The PIP signal is sent from the ICM to the PCM, which will use the PIP signal to determine base ignition
timing and rpm calculations.
The ICM also receives the Spark Angle Word (SAW) signal from the PCM, which is used by the ICM to
calculate the proper spark timing advance. Once all of the signals are calculated, the ICM determines the
proper ON and OFF timing for the ignition coils.
The 4.0L engine utilizes one ignition coil pack, which contains three separate ignition coils. Each ignition coil
fires two spark plugs simultaneously. One of the two plugs being fired is on the compression stroke (this plug
uses most of the voltage) and the other plug is on the exhaust stroke (this plug uses very little of the voltage).
Since these two plugs are connected in series, the firing voltage of one plug is negative (with respect to HOW TO USE THIS BOOK
186 SYSTEM OPERATION 
						

							
ground) and the other plug is positive.
If, for some reason, a fault arises in the EI system, the Failure Mode Effects Management (FMEM) portion of
the ICM maintains vehicle operation. If the ICM stops receiving the SAW input signal, it will directly fire the
ignition coils based on the CKP signal. This condition results in a fixed timing of 10 degrees BTDC.
EEC-V Systems
The CKP signal is sent to the PCM, which uses the signal to determine base ignition timing and rpm
calculations.
The one missing tooth on the data wheel creates one large space between two of the teeth. The PCM utilizes
this large space as a reference to help determine base ignition timing and engine speed (rpm), and to
synchronize the ignition coils for the proper spark timing sequence.
All engines, except the 2.3L, 2.5L and 5.0L engines, utilize one ignition coil pack, which contains three
separate ignition coils, whereas the 2.3L, 2.5L and 5.0L engines use two separate ignition coil packs, each of
which contains two ignition coils. Each ignition coil fires two spark plugs simultaneously. One of the two
plugs being fired is on the compression stroke (this plug uses most of the voltage) and the other plug is on the
exhaust stroke (this plug uses very little of the voltage). Since these two plugs are connected in series, the
firing voltage of one plug is negative (with respect to ground) and the other plug is positive.
Diagnosis and Testing
SERVICE PRECAUTIONS Always turn the ignition key OFFand isolate both ends of a circuit whenever testing for shorts or
continuity.
· 
Never measure voltage or resistance directly at the processor connector.
· 
Always disconnect solenoids and switches from the harness before measuring for continuity,
resistance or energizing by way of a 12-volt source.
· 
When disconnecting connectors, inspect for damaged or pushed-out pins, corrosion, loose wires, etc.
Service if required.
· 
PRELIMINARY CHECKS Visually inspect the engine compartment to ensure that all vacuum lines and spark plug wires are
properly routed and securely connected.
1. 
Examine all wiring harnesses and connectors for insulation damage, burned, overheated, loose or
broken connections.
2. 
Be certain that the battery is fully charged and that all accessories are OFFduring the diagnosis.
3. 
GENERAL SYSTEM TEST
This is a general system test for a no-start condition. Use the accompanying flow charts for this test. For
ignition coil testing refer to the ignition coil procedures.
Most Digital Volt Ohmmeters (DVOMs) used today belong to a class referred to as averaging. Some
averaging DVOMs include the Rotunda® 007-00001, the Fluke® 70, 20 series and the Fluke® 88. HOW TO USE THIS BOOK
SYSTEM OPERATION 187 
						

							
Recently a new class of DVOMs, referred to as True RMS DVOMs (such as: the Fluke® 87, 8060A,
8062A, etc.), are being used. True RMS DVOMs should not be used for the tests presented here. They
may display different voltage readings depending on whether the DVOM is first turned on and then the
test leads are attached, or if the leads are attached first, then the DVOM is turned on. Also they may
not auto range to the same range during each test, and some show different values depending on the
range selected.
Test A-no start, part 1Click to enlarge
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188 GENERAL SYSTEM TEST 
						

							Test A-no start, part 2
Click to enlarge
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GENERAL SYSTEM TEST 189