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 spitting 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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• | Check for a contaminated fuel condition. Refer to Alcohol/Contaminants-in-Fuel Diagnosis
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Sensor/System
| Use a scan tool in order to monitor the KS system for excessive spark retard
activity.
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Ignition System
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• | 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. |
• | Check for proper ignition voltage output with spark tester J 26792
. |
• | Remove the spark plugs and check for the following: |
Refer to
Spark Plug Visual Diagnosis
in Engine Electrical.
• | Visually/Physically inspect the Secondary ignition for the following: |
- | Ignition wires arcing to ground |
- | Ignition wires for proper engagement to spark plug. |
- | Ignition coils for cracks or carbon tracking |
• | Monitor the Misfire Current Counters while driving the vehicle
in the conditions that the misfire occurred. If a cylinder can be located
with a misfire use the DTC P0300 table for diagnosis. |
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Engine Mechanical
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• | Check engine mechanical for the following: |
- | Excessive oil in combustion chamber-Leaking valve seals. Refer
to Oil Consumption Diagnosis
in Engine Mechanical 4.8L, 5.3L, 6.0L. |
• | For incorrect basic engine parts. Inspect the following: |
Refer to Engine/Engine Mechanical for diagnosis procedures.
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Additional
Checks
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• | Check the exhaust system for possible restrictions. Check for
the following: |
- | Inspect the exhaust system for damaged or collapsed pipes. |
- | Inspect the exhaust manifold for a collapsed inner wall. |
- | Inspect the mufflers for heat distress or possible internal failure. |
- | Inspect for possible plugged Three-Way catalytic converters by
comparing exhaust system back pressure on each side of engine. Check back
pressure by removing AIR check valves near exhaust manifolds.
Refer to
Restricted Exhaust System Check
in Engine Exhaust. |
• | Electromagnetic Interference (EMI) on the reference circuit can
cause an engine miss condition A sudden increase in indicated RPM with little
change in actual engine RPM change indicates EMI is present.
Check for high voltage components near Ignition Control circuits
if a problem exists. |
• | Check the intake manifold and the exhaust manifold passages for
casting flash. Refer to Engine/Engine Mechanical. |
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