Checks
| Action
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DEFINITION: A steady
pulsation or jerking that follows engine speed, which is usually more pronounced
as the 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 at low speed.
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Preliminary
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• | Refer to Important Preliminary Inspections Before Starting in
Symptoms
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Fuel System
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• | Inspect for a contaminated fuel condition. Refer to Alcohol/Contaminants-in-Fuel Diagnosis
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Sensor/System
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- Use a scan tool in order to monitor the KS system for excessive
spark retard activity. Refer to
Knock Sensor (KS) System Description
.
- An Extended Travel Brake Switch that is mis-adjusted or an Extended
Travel Brake circuit that is open causes a perceived misfire under heavy load
conditions from a stop. Use a scan tool in order to monitor the Extended
Travel Brake Switch parameter. If the scan tool displays Extended Travel
Brake Switch applied when the brake pedal is released refer to
DTC P1575 Extended Travel Brake Switch Circuit
.
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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. |
• | Test for proper ignition voltage output with spark tester J 26792
. |
• | Remove the spark plugs and inspect for the following conditions: |
• | An improper spark plug gap will cause a driveability concern.
Gap the spark plugs using a wire gauge gap tool (J 41319). Refer
to
Spark Plug Replacement
in Engine Electrical. |
• | Visually/Physically inspect the secondary ignition for the following: |
- | Ignition coils for cracks or carbon tracking |
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Engine Mechanical
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• | Inspect engine mechanical for the following: |
- | Test compression. Refer to Engine Compression Test
in Engine Mechanical-5.7L. |
• | For incorrect basic engine parts, inspect the following components: |
• | Refer to Engine Mechanical for diagnosis procedures. |
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Additional Checks
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• | Inspect the exhaust system for possible restrictions. Perform
for the following: |
• | 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 that EMI is present. Inspect
for high voltage components near the ignition control circuits if
a condition exists. |
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