Checks
| Action
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DEFINITION: Steady pulsation or jerking that follows engine speed, usually
more pronounced as engine load increases.
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Preliminary
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Fuel System
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• | Check items which can cause an engine to run rich (long term
fuel trim significantly in the negative range). Refer to Diagnostic Aids for
DTC P0172. |
• | Check items that can cause an engine to run lean (long term fuel
trim significantly in the positive range). Refer to Diagnostic Aids for DTC P0171. |
• | Check for fuel in the Fuel Pressure Regulator vacuum hose. |
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Sensor/System
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• | Check for conditions which cause an incorrect idle speed. |
- | Throttle body tampering, excessive deposits, or damage. Refer
to Fuel Supply Component Description
. |
- | Restricted air intake system. |
• | Check the TP Sensor and related circuit wiring. Refer to DTC P0123
Diagnosis. |
• | Check the EGR system for proper operation. Refer to EGR System Description
. |
• | Check the PCV Valve for proper operation. Refer to Crankcase Ventilation System Description
. |
• | Check the Transaxle Range Switch input with the vehicle in drive
and the gear selector in drive or overdrive. |
• | Check the following for damage: |
• | Bent harmonic balancer interrupter rings. |
• | Damaged Crankshaft Position Sensor. |
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Ignition System
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• | Check for proper ignition voltage output using the following steps: |
- | Clip the J 26792
Spark
Tester to engine ground. |
- | Connect one end of a spark plug wire to the J 26792
Spark Tester, leave the other end of
the spark plug wire to the coil being tested. |
- | Connect one end of another spark plug wire to the other coil
tower; connect the other end of the spark plug wire to ground. |
- | Crank the engine while observing the J 26792
Spark Tester; a spark should be observed. |
- | Repeat the above steps for each coil. |
• | If adequate spark is not present at the coil(s), check for the
following conditions: |
- | Coil(s)--Cracks, carbon tracking/arcing, or a resistance
value outside the specified range. |
Coil Resistance 5000-8000ohms (5K-8Kohms) - | Spark Plug wires--Signs of arcing/cross firing, cracks,
carbon tracking, plug boot damage, pinched, improper routing, or a resistance
value outside the specified range. |
Spark Plug Wire Resistance 600ohms per foot (1 968ohms per meter).
| Important: : Spraying the secondary ignition wires with a light mist of water may
help locate an intermittent problem. Ignition components will arc to ground
when a secondary component is faulty.
|
- | Ignition System Wiring--Loose ignition module feed or ground
connection, or damaged system wiring. |
• | Remove spark plugs and check for the following: |
- | Burned or damaged electrodes |
- | Improper heat range or reach |
• | If spark plugs are gas or oil fouled, the cause of the fouling
must be determined before replacing the spark plugs. |
• | Check for the following intermittent ignition system conditions: |
- | Intermittent CKP 24X Signal. |
- | Intermittent ignition feed circuit or sensor ground circuit to
the crankshaft position sensor or the camshaft position sensor. |
- | Intermittent 3X reference signal. |
- | Intermittent camshaft position signal |
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Engine Mechanical
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• | Check engine mechanical for the following: |
- | Sticking or leaking valves. |
- | Excessive oil in combustion chamber--Leaking valve seals.
Refer to Oil Consumption Diagnosis
in Engine Mechanical. |
- | Low cylinder compression. Refer to Engine Compression Test
in Engine Mechanical. |
• | For incorrect basic engine parts. Inspect the following: |
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Additional Checks
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• | Check exhaust system for possible restrictions. Check for the
following: |
- | Inspect exhaust system for damaged or collapsed pipes. |
- | Inspect mufflers for heat distress or possible internal failure. |
• | An engine miss condition can be caused by Electromagnetic Interference
(EMI) on the reference circuit. EMI can usually be detected by monitoring
engine RPM with a scan tool. A sudden increase in RPM with little change
in actual engine RPM change, indicates EMI is present. If a problem
exists, check routing of secondary ignition wires, high voltage components
(Near Ignition Control circuits). |
• | Check for intake and exhaust manifold passages for casting flash. |
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