| 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. |
| Preliminary |
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| Sensor/System |
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| Ignition System |
- 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:
- Correct heat range
- Wet plugs
- Cracks
- Wear
- Improper gap
- Burned electrodes
- Heavy deposits
- Verify that the spark plugs are of the correct type.
- Inspect for proper ignition system output. Refer to Electronic Ignition (EI) System Diagnosis
.
- 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 |
- Inspect engine mechanical for the following conditions:
- Compression
- Sticking or leaking valves
- Worn camshaft lobes
- Valve timing
- Worn rocker arms
- Broken valve springs
- 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:
- Refer to Symptoms - Engine Mechanical
in Engine Mechanical for diagnosis procedures.
- 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 Camshaft Cleaning and Inspection
in Engine Mechanical. This could result in any of the following conditions:
- A no start
- A start and stall
- Erratic performance
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| Additional Inspections |
- 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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