MITCHELL 1 ARTICLE - I - SYSTEM/COMPONENT TESTS 1991 ENGINE PERFORMANCE Ford Motor Co. - Ford/Merc... Page 3 of 7
POWER STEERING PRESSURE SWITCH
1. Start engine and run it at idle. Remove connector from switch. Connect ohmmeter to switch terminals. Turn steering wheel from side to
side while observing ohmmeter.
2. Replace power steering switch if continuity does not exist with front wheels turned, or if continuity exists with wheels straight ahead.
THROTTLE POSITION SENSOR (1.6L)
Unplug connector from sensor. Connect ohmmeter to sensor terminals TP and SIGRTN (Orange and Blue/Yellow wires on mating connector).
Measure resistance at each throttle opening specified in THROTTLE POSITION SENSOR RESISTANCE . Replace sensor if resistance is
not within specification.
THROTTLE POSITION SENSOR RESISTANCE
Throttle Opening
1/8
1/4
3/8
1/2
5/8
3/4
7/8
Fully Open
(1) Ohms
989
1104
1278
1462
1480
1459
1144
1072
(1) Resistance may vary by plus or minus 15 percent.
THROTTLE POSITION SWITCH (1.3L)
1. Ensure idle speed and ignition timing are adjusted to specification. Stop engine. Disconnect negative battery cable.
CAUTION:
DO NOT tamper with throttle stop screw at throttle lever. Doing so may result in damage to the
throttle body.
2. Unplug TPS connector at throttle body. Insert appropriate feeler gauge between throttle stop screw and stop lever. Check for continuity
between specified terminals on TPS connector. See ON-VEHICLE ADJUSTMENTS article and TPS CONTINUITY table.
TPS CONTINUITY
Test Condition (1)
.02" (.5 mm)
.03" (.7 mm)
Wide Open Throttle
Cont. Between IDL-TL
Yes
No
No
Cont. Between PSW-TL
No
No
Yes
(1) Insert specified feeler gauge between throttle adjustment screw and stop lever.
VANE AIRFLOW (VAF) METER
1. Check all wiring, harnesses, connectors and components for evidence of damage, overheating, shorting or looseness. If any defect exists,
repair as necessary.
2. Inspect vane airflow meter for damage and ensure measuring plate moves smoothly. Install BOB. Turn ignition on. Measure voltage
between BOB test pins VAF and ground on 1.3L, or between VAF and SIGRTN on 1.6L. Voltage measurements must be as specified in
VANE AIRFLOW METER VOLTAG .
VANE AIRFLOW METER VOLTAGE
Door Opening
Fully Closed
1/8
1/4
3/8
1/2
5/8
3/4
7/8
Fully Open
(1) Volts: 1.3L
.5-1.5
.59
1.19
1.78
2.38
2.97
3.56
4.16
4.5-5.0
(1) Volts: 1.6L
(2) *
3.24
5.60
5.62
5.83
6.02
6.57
7.48
7.87
(1) Voltage may vary by plus or minus 15 percent.
(2) Voltage not specified.
VANE AIR TEMPERATURE (VAT) SENSOR
1. Unplug connector from VAF meter. On 1.3L, connect ohmmeter to terminals VAT and ground (Green/Black and Black wires on mating
connector). On 1.6L, connect ohmmeter to VAF meter terminals VAT and SIGRTN (Brown and Blue/Yellow wires on mating
connector).
2. Measure intake air temperature. Measure resistance between specified terminals. See VANE AIR TEMPERATURE RESISTANCE .
Replace VAF if resistance is not as specified.
http://www.eautorepair.net/app/PrintItems.asp?S0=2097152&S1=0&SG=%7B7DD6473C%2DB5BB%2D4F20%2D9D70%2D...
3/10/2009
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