Checks
| 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
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• | Refer to Important Preliminary Checks Before Starting in
Symptoms
. |
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Sensor/System
|
• | Check the PCV system for proper operation. |
• | Check the throttle body, and TP sensor for proper operation and
damage. |
• | Check the knock system (KS) for excessive spark retard. |
• | Check the EGR system for proper operation. |
• | Check the IAC valve and valve housing for deposits and/or damage. |
• | Check for dirty or damaged air cleaner element. |
• | Check for collapsed or damaged intake air ducting. |
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Fuel System
|
• | Check the fuel injectors and related wiring. Refer to: |
• | Check the minimum idle speed. |
• | Check for items that cause the engine to run rich, or lean. |
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Ignition System
|
• | Check the IC circuits for proper connections at each ignition
module assembly. |
• | Check for proper ignition voltage output using the J 26792
spark tester. |
• | Check the ignition coils for cracks, or damage. |
• | Check for a missing or damaged ignition module assembly grounding
spring. |
• | Check for misaligned, or damaged spark plug boots. |
| Important: If the spark plugs are gas or oil fouled, the cause of the fouling must
be determined before replacing the spark plugs.
|
• | Check the spark plugs for the following conditions: |
- | Improper heat range or reach |
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Engine Mechanical
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- | Sticking or leaking valves |
- | Broken or weak valve springs |
• | Check for incorrect basic engine parts. Inspect the following: |
- | Pistons, etc. Refer to Engine Mechanical. |
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Additional Checks
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• | Check the exhaust system for possible restrictions. |
• | Check for fuel loading in the EVAP system. |
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