Cuts Out, Misses Symptom
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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Sensor Checks
| Inspect the mass air flow (MAF) sensor operation. Run the engine to
normal operating temperature. Turn OFF all accessories and observe the MAF
sensor at idle with a scan tool. If the MAF sensor reading is more than
3.5 g/s refer to
DTC P0101 Mass Air Flow (MAF) Sensor Performance
.
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Fuel System Checks
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• | Check for water contamination of the fuel. |
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Ignition
System Checks
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• | Check for an ignition system misfire: |
| Important: Do not perform this test for more than 2 minutes in order to
prevent damage to the catalytic converter.
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2. | Remove one ignition coil at a time using insulated pliers. |
4. | Check for spark on the suspected cylinders with a J 26792
spark tester or equivalent if there
is no RPM drop on one or more cylinders. |
6. | If there is spark, check the spark plugs for any of the following
conditions: |
- | Any wet or fuel fouled plugs |
- | A terminal screw that is bent or loose |
- | A ceramic insulator that has cracks, carbon tracking, or red or
black dust deposits. |
- | A tip insulator that has cracks or carbon tracking, any oil, carbon,
glazing, or fuel additive deposits, or is loose. |
- | A center electrode that is loose and wiggles side to side. |
- | An incorrect spark plug gap |
• | Check the ignition coil boots for carbon tracking or cracks. |
• | Check the ignition system for moisture, dust, cracks, burns, etc. |
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Engine Mechanical Checks
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• | Check for any of the following engine mechanical problems: |
- | Any faulty hydraulic lifter assemblies |
- | 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. |
• | Refer to Engine Mechanical. |
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Additional Checks
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• | An engine miss condition can be caused by electromagnetic interference
(EMI) on the reference circuit. EMI can usually be detected by monitoring
the engine RPM with a scan tool. A sudden increase in RPM with little
change in the actual engine RPM change indicates EMI is present.
If a problem exists, check the routing of the secondary ignition
wires and the high voltage components. |
• | Verify the PCM grounds are clean, tight, and in the proper locations.
Refer to
Power and Ground
. |
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