| DEFINITION: A steady pulsation or jerking that follows engine speed, which is usually more pronounced as the engine load increases. This condition is not normally felt above 1500 RPM or 48 km/h (30 mph). The exhaust has a steady spitting sound at idle or at low speed. |
| Preliminary |
- Refer to Important Preliminary Inspections Before Starting in Symptoms - Engine Controls .
- Search for bulletins.
- Verify that the engine control module (ECM) grounds are clean, tight, and in the proper locations.
- Remove the air filter element and inspect for restrictions. Refer to Air Cleaner Element Replacement
and replace if necessary.
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| Fuel System |
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| Sensor/System |
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| Ignition System |
- 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/listen for arcing or misfiring as water is applied.
- Test the ignition voltage output with the J 26792
Spark Tester. Refer to Electronic Ignition (EI) System Diagnosis .
- Remove the spark plugs and inspect for the following conditions:
- An improper spark plug gap will cause a driveability concern. Refer to Ignition System Specifications
.
- If the spark plugs are fouled by gas, coolant, or oil, determine the cause before replacing the plugs. Refer to the following procedures:
- Inspect the spark plug wires for damage.
- Test the crankshaft position (CKP) sensor for the correct resistance. The CKP sensor resistance may be out of range after a hot soak. The resistance should be between 460-620 ohms.
- Inspect the ignition coil for cracks or carbon tracking.
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| Engine Mechanical |
- Inspect for the following engine mechanical conditions:
- Inspect the following for incorrect basic engine parts:
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| Additional Checks |
- Inspect the following exhaust system components:
- Electromagnetic interference (EMI) on the reference circuit can cause a misfire condition. You can usually detect EMI with a scan tool by monitoring the engine speed parameter. A sudden increase in the engine speed parameter with little change in actual engine speed indicates that EMI is present. Inspect the high voltage components near the ignition control circuit if a condition exists.
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