Inspections
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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
1,500 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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Fuel Systems
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• | Inspect for the following conditions that may cause the engine to run
rich: |
Notice: Refer to Heated Oxygen and Oxygen Sensor Notice in the Preface section. - | Water intrusion in the heated oxygen sensor (HO2S) connector |
- | Purging of a saturated evaporative emission (EVAP) canister |
- | Vacuum hoses that are split, kinked, or improperly connected |
- | An air intake duct that is collapsed or restricted |
• | Inspect for the following conditions that may cause the engine to run
lean: |
Notice: Refer to Heated Oxygen and Oxygen Sensor Notice in the Preface section. - | Water intrusion in the HO2S connector |
- | An exhaust leak between the HO2S and the engine--Refer to
Exhaust Leakage
in Engine Exhaust. |
- | Vacuum hoses that are split, kinked, or improperly connected |
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Sensor/System
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• | Use a scan tool in order to monitor the knock sensor (KS) system for excessive
spark retard activity. Refer to
Scan Tool Data List
. |
• | Inspect for throttle body tampering, excessive deposits, or damage. |
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Ignition System
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• | In order to properly inspect the spark plugs or to correct a condition,
refer to the following procedures: |
• | Inspect for proper secondary ignition voltage output with J 26792
HEI Spark Tester. |
• | An improper spark plug gap will cause a driveability condition. Gap the
spark plugs using a wire gage gap tool. |
• | If the spark plugs are found to be fouled, determine the cause before
replacing the spark plugs. |
• | Inspect for damaged or misaligned spark plug boots. |
• | Monitor the Misfire Current Counters while driving the vehicle in the
conditions that the symptom occurred. If a misfiring cylinder can be located, use
the DTC P0300 table for diagnosis. Refer to
DTC P0300
. |
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Engine Mechanical
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• | Inspect engine mechanical for the following: |
- | Sticking or leaking valves |
- | Excessive oil in combustion chamber or leaking valve seals. |
- | For more information, refer to one or more of the following procedures in Engine Mechanical: |
• | For incorrect, worn, or damaged basic engine parts, inspect the following: |
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Additional Inspections
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• | Inspect the exhaust system for possible restrictions. Inspect for the
following: |
- | Inspect the exhaust system for damaged or collapsed pipes. |
- | Inspect the mufflers for heat distress or possible internal failure. |
- | Inspect for possible plugged catalytic converters. Refer to
Restricted Exhaust
in Engine Exhaust. |
• | Electromagnetic interference (EMI) can cause an engine misfire condition.
A sudden increase in indicated RPM parameter 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. |
• | Inspect the intake manifold and the exhaust manifold passages for casting
flash. |
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