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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• | Search for bulletins. |
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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 |
- | An inaccurate mass air flow (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
. |
- | An inaccurate MAF sensor |
- | 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: |
Refer to
Spark Plug Inspection
.
• | Determine the cause of the fouling before replacing the spark plugs. |
• | Visually and physically inspect the secondary ignition for the following: |
- | 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: |
- | Sticking or leaking valves |
• | For incorrect basic engine parts inspect the following: |
• | 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
.
This could result in any of the following conditions: |
Refer to
Symptoms - 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. |
• | 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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