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 heated oxygen sensor (HO2S) connector |
- | Engine oil contaminated by fuel |
- | An evaporative emission (EVAP) canister purge condition |
- | Vacuum hoses that are split, kinked, or improperly connected |
- | 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. |
- | Vacuum hoses that are split, kinked, or improperly connected |
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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 throttle position (TP) sensor and related wiring. Refer to
DTC P0106
. |
• | 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: |
• | Remove spark plugs and inspect for the following: |
- | Verify that the spark plugs are of the correct type. |
• | Inspect for proper ignition voltage output with the J 26792
Spark Tester. |
• | An improper spark plug gap will cause a driveability condition. Gap the
spark plugs using a wire gage gap tool. |
• | Determine the cause of the fouling before replacing the spark plugs. |
• | Inspect for damaged or misaligned spark plug boots. |
• | Inspect the electronic ignition (EI) module for 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 - 2.2L: |
• | For incorrect basic engine parts, inspect the following: |
• | Inspect for excessive crankshaft endplay that will cause the crankshaft
position (CKP) sensor reluctor wheel to move out of alignment with the CKP sensor.
Refer to
Crankshaft and Bearing Cleaning and Inspection
in Engine Mechanical - 2.2L (L61). This could result in any of
the following conditions: |
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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 miss condition. A scan tool can usually detect EMI by monitoring the engine
RPM. A sudden increase in RPM 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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