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
Symptoms , Important Preliminary Checks Before Starting.
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• | Check the PCM grounds for being clean, tight and in their proper
locations. Refer to PCM wiring diagrams
. |
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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.
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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: |
- | Correct heat range. Refer to Engine Electrical/Spark
Plugs
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• | An improper spark plug gap will cause a driveability problem.
Refer to Engine Electrical/Spark Plugs
. Do the spark
plug gapping using a wire gauge gap tool (J 41319). Refer to Spark
Plug Replacement. Determine the cause of the fouling before replacing the
spark plugs if the spark plugs are gas or oil fouled. Refer to
DTC P0172 Fuel Trim System Rich Bank 1
and
DTC P0175 Fuel Trim System Rich Bank 2
for
diagnosis of the rich condition or Engine/Engine Mechanical
for diagnosis of the oil fouling condition. |
• | Visually/Physically inspect the Secondary ignition for the following: |
- | Ignition wires for cross firing |
- | 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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• | Check engine mechanical for the following: |
- | Sticking or leaking valves |
- | Excessive oil in combustion chamber-Leaking valve seals |
- | Low cylinder compression |
• | 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 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
and Engine/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. Check routing of secondary
ignition wires, 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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