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 a idle or low speed.
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Preliminary
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Fuel System
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• | Inspect 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 the HO2S connector |
- | Engine oil contaminated by fuel |
- | an evaporative emission (EVAP) canister purge condition |
- | Vacuum hoses for splits, kinks and proper connections |
• | Inspect the following 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 for splits, kinks and proper connections |
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Sensor/System
| Monitor the knock sensor for excessive spark retard with a scan tool.
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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 and listen for arcing or misfiring as you apply water. |
• | Test for proper ignition voltage output with J 26792
spark tester . |
• | An improper spark plug gap will cause a driveability problem. Gap the
spark plugs using a wire gage gap tool. Refer to
Spark Plug Replacement
. |
• | Determine the cause of the fouling before replacing the spark plugs
if the spark plugs are gas, coolant, or oil fouled. Refer to
Spark Plug Inspection
for diagnosis of fouled spark plugs. |
• | Monitor the Misfire Current Counters while driving the vehicle in the
conditions that the misfire occurred. If a cylinder can be located with a misfire,
refer to
Electronic Ignition (EI) System Diagnosis
for diagnosis. |
• | Visually and physically inspect the secondary ignition for the following: |
- | Spark plug wires arcing to ground |
- | Spark plug wires for proper engagement to spark plug |
- | Ignition coils for cracks or carbon tracking |
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Engine Mechanical
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• | Inspect engine mechanical for the following: |
- | Sticking or leaking valves |
• | Inspect the following components for incorrect basic engine parts. Refer
to the appropriate procedures in Engine Mechanical for diagnosis procedures: |
• | Inspect for excessive crankshaft endplay that will cause the 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
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• | Inspect the following components of the exhaust system for possible
restrictions: |
- | The exhaust system for damaged or collapsed pipes |
- | The exhaust manifold for a collapsed inner wall |
- | The mufflers for heat distress or possible internal failure |
- | Compare 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 miss condition. A sudden increase in the engine speed parameter on the
scan tool 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 problem exists. |
• | Inspect the intake manifold and the exhaust manifold passages for casting
flash. |
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