Checks
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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.
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Preliminary
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• | 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. |
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Fuel System
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• | Test or inspect items that can cause an engine to run rich. For a rich condition, refer to
DTC P0172
. |
• | Test or inspect items that can cause an engine to run lean. For a lean condition, refer to
DTC P0171
. |
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Sensor/System
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• | An incorrect idle may be causing the condition. |
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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/listen for arcing or misfiring as water is applied. |
• | Remove the spark plugs and inspect for the following conditions: |
- | Refer to the following procedures: |
• | If the spark plugs are fouled by gas, coolant, or oil, determine the cause before replacing the plugs. Refer to the following procedures: |
- | For diagnosis of a rich condition, refer to
DTC P0172
. |
• | 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
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• | Inspect for the following engine mechanical conditions: |
- | Excessive oil in the combustion chamber or leaking valve seals |
- | Incorrect cylinder compression |
- | Sticking or leaking valves |
- | Excessive carbon buildup in the combustion chambers. Clean the chambers with top engine cleaner. Follow the instructions on the can. |
- | For more information, refer to the following procedures in Engine Mechanical - 1.2L: |
• | Inspect the following for incorrect basic engine parts: |
- | The pistons, connecting rods, and bearings |
- | Refer to the following procedures in Engine Mechanical - 1.2L: |
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Additional Checks
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• | Inspect the following exhaust system components: |
- | The exhaust system for physical damage |
- | The mufflers for heat distress or possible internal failure |
- | The three-way catalytic converter(s) for restrictions. |
• | 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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