Inspection/Test
| 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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| • | Inspect any items which may cause an engine to run rich, long
term fuel trim significantly in the negative range. Refer to Diagnostic Aids
for DTC P0172. |
| • | Inspect any items which may cause an engine to run lean, long
term fuel trim significantly in the positive range. Refer to Diagnostic Aids
for DTC P0171. |
| • | Inspect for fuel in the fuel pressure regulator vacuum hose. |
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Sensor/System
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| • | Inspect for any conditions which cause an incorrect idle speed: |
| - | Restricted air intake system |
| • | Test the transaxle range switch input with the vehicle in drive
and the gear selector in drive or overdrive. |
| • | Inspect the following components for damage: |
| • | Bent harmonic balancer interrupter rings |
| • | Damaged crankshaft position (CKP) sensor |
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Ignition System
|
| • | Inspect for proper ignition voltage output using the following
steps: |
| 1. | Attach the J 26792
spark tester to engine ground. |
| 2. | Connect the spark plug end of the spark plug wire to the J 26792
spark tester; leave the
other end of the spark plug wire connected to the coil being tested. |
| 3. | Connect the spark plug end of the companion spark plug wire to
ground. |
The companion spark plug wire is the wire attached to the corresponding
coil tower.
| 4. | Crank the engine while observing the J 26792
spark tester; a spark should be observed. |
| 5. | Repeat the above steps for each coil. |
| • | If spark is not present at the coils, inspect for the following
conditions: |
| - | Coils--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 voltage will arc to ground when
a secondary component is faulty.
|
| - | Defective ignition module. |
| - | Ignition system wiring--Loose ignition module feed or ground
connection, or damaged system wiring. |
| • | Remove spark plugs and inspect for the following conditions: |
| - | 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. |
| • | Inspect for the following 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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| • | Inspect the engine mechanical for the following conditions: |
| - | Sticking or leaking valves |
| - | Excessive oil in combustion chamber or leaking valve seals |
| - | Low cylinder compression |
| • | Inspect the following components for incorrect basic engine
parts: |
|
Additional
|
| • | Inspect exhaust system for possible restrictions. Inspect 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, inspect routing of secondary
ignition wires, high voltage components, near Ignition Control
circuits. |
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