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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Sensor/System
|
| • | Check the throttle body, and throttle position (TP) sensor for
proper operation and damage. |
| • | Check the knock system (KS) for excessive spark retard. |
| • | Check the exhaust gas recirculation (EGR) system for proper operation. |
| • | Check the idle air control (IAC) valve and valve housing for deposits
and/or damage. |
| • | Check for dirty or damaged air cleaner element. |
| • | Check for collapsed or damage intake air ducting. |
|
Fuel System
|
| • | Check the fuel injectors and related wiring. Refer to the following: |
| • | Check the minimum idle speed. |
| • | Check for items that cause the engine to run rich, or lean. |
|
Ignition System
|
| • | Check the ignition control (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. |
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Engine Mechanical
|
| - | Sticking or leaking valves |
| - | Broken or weak valve springs |
| - | Excessive oil in the combustion chamber-leaking valve seals |
| • | Check for incorrect basic engine parts. Inspect the following: |
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Additional Checks
|
| • | Check the exhaust system for possible restrictions. Refer to
Restricted Exhaust
in Engine Exhaust. |
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