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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Fuel System
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• | Inspect for the following 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 |
- | Engine oil contaminated by fuel |
- | An evaporative emission (EVAP) canister purge condition |
- | Blockage on the inlet screen of the MAF sensor |
- | Vacuum hoses that are split, kinked, or improperly connected |
• | 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
| Use a scan tool in order to monitor the knock sensor (KS) system for excessive
spark retard activity.
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Ignition System
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• | Soak the secondary ignition system with water from a spray bottle. Soaking
the secondary ignition system may help locate damaged or deteriorated components.
Look and listen for arcing or misfiring as you apply water. |
• | Test for proper ignition voltage output with the J 26792
Spark Tester . |
• | Remove the spark plugs and inspect for the following conditions: |
• | Determine the cause of the fouling before replacing the spark plugs. |
• | Visually and physically inspect the secondary ignition for the following
conditions: |
- | The ignition wires arcing to ground |
- | The ignition wires for proper engagement to spark plug |
- | The 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 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 |
• | For incorrect basic engine parts inspect the following: |
Refer to
Symptoms - Engine Mechanical
in Engine Mechanical for diagnostic procedures.
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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 by comparing the exhaust
system back pressure on each side of engine. Refer to
Restricted Exhaust
in Engine Exhaust. |
• | Electromagnetic interference (EMI) on the reference circuit 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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