Inspections
| 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
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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Sensor/System
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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. - | Any water intrusion in the heated oxygen sensor (HO2S) connector |
- | The engine oil contaminated by fuel |
- | Any 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. - | Any water intrusion in the HO2S connector |
- | An exhaust leak between the HO2S and the engine--Refer to
Exhaust Leakage
in Engine Exhaust. |
- | Any vacuum hoses that are split, kinked, or improperly connected |
• | 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: |
• | Remove spark plugs and inspect for the following conditions: |
- | Verify that the spark plugs are of the correct type. |
• | Inspect for proper ignition voltage output with the
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. |
• | Determine the cause of the fouling before replacing the spark plugs. |
• | Inspect for damaged or misaligned spark plug boots. |
• | Inspect the electronic ignition (EI) module for proper ground connection. |
• | 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 conditions: |
- | 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 basic engine parts, inspect the following components: |
• | Inspect for excessive crankshaft endplay that will cause the crankshaft
position (CKP) sensor reluctor wheel to move out of alignment with the CKP sensor.
Refer to
Crankshaft and Bearing Cleaning and Inspection
in Engine Mechanical. This could result in any of the following conditions: |
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Additional Inspections
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• | Inspect the exhaust system for the following possible restrictions: |
- | The exhaust system for damaged or collapsed pipes |
- | The mufflers for heat distress or possible internal failure |
- | The catalytic converters for being plugged--Refer to
Restricted Exhaust
in Engine Exhaust. |
• | Electromagnetic interference (EMI) can cause an engine misfire condition.
A sudden increase in indicated 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. |
• | Inspect the intake manifold and the exhaust manifold passages for casting
flash. |
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