Checks
| Action
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DEFINITION: A steady
pulsation or jerking that follows engine speed, usually more pronounced as
the engine load increases. The exhaust has a steady spitting sound at
idle, low speed or on hard acceleration.
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Preliminary Checks
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Ignition System Checks
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• | Run the engine and spray the ignition system with water in order
to check for secondary voltage shorts. |
• | Check the engine reference signal of the camshaft position (CMP)
sensor with a scan tool. Observe the Engine Speed parameter while operating
the engine at the speed of the concern. The scan tool should indicate
steady and linear RPM readings while running. If the erratic values,
such as sudden spikes or drops in engine speed are displayed, the engine
reference signal is not stable enough for the engine to run properly.
Inspect the CMP sensor signal rotor and housing for worn bushings or drive
coupling. Inspect for electromagnetic interference (EMI) of the reference
signal. |
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Engine Mechanical Checks
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• | Check for any of the following engine mechanical problems: |
- | An incorrect valve lash |
- | Any broken or weak valve springs |
- | An incorrect valve timing |
- | An incorrect or worn camshaft |
• | Check the intake and exhaust manifold passages for casting flash. |
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Fuel System Checks
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• | Check for a restriction in the fuel supply system. Check for the
correct fuel pressure. Refer to
Fuel System Diagnosis
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• | Check for water contamination of the fuel. |
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Additional
Checks
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• | Check the Service Bulletins for any updates or information. |
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