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Home >> GMC >> 1988 >> Forward Control 5.7 M, Standard >> Repair and Diagnosis >> Engine Performance >> System >> PCV System >> System Testing
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System Testing

  1. Start engine and allow it to reach normal operating temperature. Ensure engine is idling at normal curb idle. Remove PCV valve from grommet. If valve is okay, hissing will be heard as air passes through it. Strong vacuum should be felt over valve inlet.
  2. With finger over valve inlet, check for vacuum leaks at all connections. Reinstall PCV valve and remove crankcase air inlet hose at air cleaner.
  3. Loosely hold piece of stiff paper over opening at end of inlet hose. After about a minute, paper should be sucked against hose opening with noticeable force. Remove and shake PCV valve. Ensure a metallic clicking noise can be heard, indicating valve is free.
  4. If system passes both engine running and stopped tests, it is functioning properly. If it has failed either test, replace defective components and retest. If it does not pass on second try, clean system.
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