| 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.
- For incorrect basic engine parts, inspect the following components:
- Refer to Symptoms - 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
. 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
.
- 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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