Checks
| Action
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DEFINITION : Steady pulsation or jerking that follows engine
speed, usually more pronounced as engine load increases. This condition
is not normally felt above 1500 RPM or 48 km/h (30 mph).
The exhaust has a steady sputtering sound at idle or low
speed.
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Preliminary
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• | Refer to Important Preliminary Checks Before Starting in
Symptoms
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Fuel System
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Sensor/System
| Use a scan tool in order to monitor the KS
system for excessive spark retard activity. Refer to
Knock Sensor (KS) System Description
.
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Ignition System
|
• | Wet down the secondary ignition system with water from a spray
bottle. Wetting down the secondary ignition system may help locate damaged
or deteriorated components. Look/listen for arcing or misfiring
as you apply water. |
• | Remove the spark plugs and inspect for the following: |
• | An improper spark plug gap causes a driveability condition. Gap
the spark plugs using a wire gauge gap tool. Refer to
Spark Plug Replacement
in Engine Electrical. |
• | Visually/Physically inspect the secondary ignition for the following: |
- | Ignition wires arcing to ground |
- | Ignition wires for proper routing |
- | Ignition coils for cracks or carbon tracking |
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Engine Mechanical
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• | Inspect engine mechanical for the following: |
• | For incorrect basic engine parts. Inspect the following: |
- | Refer to Engine Mechanical-5.7L for diagnosis procedures. |
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Additional Checks
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• | Inspect exhaust system for possible restrictions. Inspect for
the following: |
- | Inspect the exhaust system for damaged or collapsed pipes, Refer
to
Restricted Exhaust
in Engine
Exhaust. |
- | Inspect for possible plugged Three-Way catalytic converters by
comparing exhaust system back pressure on each side of engine. Test the
back pressure by removing AIR check valves near exhaust manifolds
or the Heated Oxygen sensors. Refer to
Restricted Exhaust
in Engine Exhaust. |
• | Electromagnetic Interference (EMI) on the reference circuit can
cause an engine miss condition A sudden increase in RPM with little change
in actual engine RPM change indicates EMI is present. Inspect
for high voltage components near Ignition Control circuits
if a condition exists. |
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