F 150 4WD Pickup V8-302 5.0L (1986)
Air Cleaner Element: All Technical Service Bulletins
Engine - Lack of Power/No Start Diagnosis
Article No.
91-12-11
06/12/91
LACK OF POWER 7.5L, 5.8L, 5.0L, 4.9L - CATALYTIC CONVERTER DIAGNOSTIC TIPS
LIGHT TRUCK:
1986-91 BRONCO, ECONOLINE, F-150-350 SERIES 1988-91 F SUPER DUTY, F47
ISSUE:
Lack of power or a no start condition may be diagnosed as an exhaust restriction caused by a plugged catalytic converter. A plugged
catalytic converter (internal deterioration) is usually caused by abnormal engine operation.
ACTION:
Diagnose the catalytic converter to confirm internal failure. Refer to the Catalyst and Exhaust System Diagnostic Section, in the
Engine/Emissions Diagnostic Shop Manual and the following procedures for service details.
1.
Lack of proper HEGO operation may cause, or be the result of a rich or lean fuel condition, which could cause additional heat in the catalyst.
Perform self test KOEO and KOER, service any codes.
NOTE:
IF TWO DIGIT CODES 41, 42, 85 OR THREE DIGIT CODES 171, 172, 173, 179, 181, 182, 183 AND 565 ARE RECEIVED, CHECK
FOR PROPER HEGO GROUND.
If the HEGO ground is good, the following areas may be at fault:
^
Ignition Coil
^
Distributor Cap
^
Distributor Rotor
^
Fouled Spark Plug
^
Spark Plug Wires
^
Air Filter
^
Stuck Open Injector
^
Fuel Contamination Engine OIL
^
Manifold Leaks Intake/ Exhaust
^
Fuel Pressure
^
Poor Power Ground
^
Engine Not At Normal Operating Temperature
^
HEGO Sensor
2.
Spark timing that is retarded from specification may increase exhaust gas temperature and shorten catalyst life. Refer to the following
procedure for service details.
a.
Check spark timing. Check base timing with spout disconnected. Set base timing to the specification on the vehicle emission decal.
b.
Check computed timing with spout connected.
NOTE:
COMPUTED TIMING IS EQUAL TO BASE TIMING PLUS 20~ BTDC +/- 3~.
3.
Misfiring spark plugs may cause an unburned fuel air mixture to pass through the catalyst, which could cause higher than normal catalyst
temperatures. Refer to the following procedure for service details.
a.
Check secondary ignition, hook the vehicle up to an engine analyzer and check for a secondary ignition misfire.
