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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