Inspections
| Action
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DEFINITION: Engine runs unevenly at idle. If severe, the engine or vehicle
may shake. Engine idle speed may vary in RPM. Either condition may be severe enough
to stall the engine.
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Preliminary Inspections
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Fuel System
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• | Inspect that each fuel injector harness is connected to the correct injector/cylinder.
Relocate fuel injector harnesses as necessary. |
• | Inspect for the following that may cause the engine to run rich: |
Notice: Refer to Heated Oxygen and Oxygen Sensor Notice in the Preface section. - | Water intrusion in the HO2S connector |
- | Purging of a saturated EVAP canister |
- | Vacuum hoses that are split, kinked, or improperly connected |
- | Proper operation of the MAP sensor--Refer to
DTC P0105
. |
- | An air intake duct that is collapsed or restricted |
• | Inspect for the following conditions that may cause the engine to run
lean: |
Notice: Refer to Heated Oxygen and Oxygen Sensor Notice in the Preface section. - | Water intrusion in the HO2S connector |
- | An exhaust leak between the HO2S and the engine--Refer to
Exhaust Leakage
in Engine Exhaust. |
- | Proper operation of the MAP sensor--Refer to
DTC P0105 |
- | Vacuum hoses that are split, kinked, or improperly connected |
|
Sensor/System
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• | Test for conditions which cause an incorrect idle speed. |
- | Throttle body tampering, excessive deposits, or damage |
- | Restricted air intake system |
• | Inspect the crankcase ventilation system for proper operation. Refer toCrankcase Ventilation System Inspection/Diagnosis
in Engine Mechanical. |
• | Monitor the knock sensor (KS) system for excessive spark retard activity
with a scan tool. |
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Ignition System
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• | In order to properly inspect the spark plugs or to correct a condition,
refer to the following procedures: |
• | Inspect for proper secondary ignition voltage output with the J 26792
(SA9199Z) Spark Tester. |
• | An improper spark plug gap will cause a driveability condition. Gap the
spark plugs using a wire gage gap tool. |
• | If the spark plugs are found to be fouled, determine the cause before
replacing the spark plugs. |
• | Inspect for damaged or misaligned spark plug boots. |
• | Inspect the electronic ignition (EI ) module for a proper ground connection. |
• | Monitor the Misfire Current Counters while driving the vehicle in the
conditions that the symptom occurred. If a misfiring cylinder can be located, use
the DTC P0300 table for diagnosis. Refer to
DTC P0300
. |
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Engine Mechanical
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• | Inspect engine mechanical for the following: |
- | Sticking or leaking valves |
- | Excessive oil in combustion chamber or leaking valve seals. |
- | For more information, refer to one or more of the following procedures in Engine
Mechanical: |
• | For incorrect, worn, or damaged basic engine parts, inspect the following: |
Refer to
Symptoms - Engine Mechanical
in Engine Mechanical for diagnosis procedures.
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Additional Inspections
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• | Inspect the exhaust system for possible restrictions. Inspect for the
following: |
- | The exhaust system for damaged or collapsed pipes |
- | The mufflers for heat distress or possible internal failure |
• | Electromagnetic interference (EMI) on the reference circuit can cause
an engine misfire condition. A scan tool can usually detect EMI by monitoring the
engine RPM. A sudden increase in RPM parameter with little change in actual engine
RPM change indicates that EMI is present. If a condition exists, inspect routing
of secondary ignition wires or high voltage components near the ignition control
circuits. |
• | Inspect the intake manifold and the exhaust manifold passages for casting
flash. |
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