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Home >> Chevrolet >> 2002 >> Blazer 4D Utility, 4WD, Part Time >> Repair and Diagnosis >> External Pages >> Different car >> Section 1374 (Vibration Symptoms Diagnosis And Correction) >> Diagnostic Information and Procedures >> Engine Order Classification >> Engine First Order Classification

Engine First Order Classification

WARNING: This page is about a different car, the 2004 Pontiac Vibe. However, it is still accessible from the selected car via links, so may be relevant.
  1. Convert the engine speed (in revolutions per minute, RPM) recorded during duplication of the disturbance into Hertz (revolutions per second, RPS), by dividing the RPM by 60 (seconds). Refer to the following example:

    1200 RPM divided by 60 = 20 Hz (or RPS)

  2. Compare the dominant frequency (Hz) recorded during duplication of the disturbance with the engine speed just converted (into Hz), to determine if they are related.
  3. If the dominant frequency (Hz) recorded during duplication of the disturbance and the engine speed (converted into Hz) ARE related, then an engine FIRST ORDER related disturbance is present. (Engine first order disturbances are usually related to an imbalanced component.) Refer to the Engine Order Related Disturbances table.
  4. If the dominant frequency (Hz) recorded during duplication of the disturbance and the engine speed (converted into Hz) are NOT related, then determine if the disturbance is related to the engine's firing frequency. Proceed to Engine Firing Frequency Classification.
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