GM Service Manual Online
For 1990-2009 cars only
  1. Raise and suitably support the vehicle with safety stands. Refer to Lifting and Jacking the Vehicle in General Information.
  2. Allow the front wheels to rotate freely.
  3. Allow the steering mechanism to turn freely.
  4. Position the wheels in a straight ahead position.
  5. Position a dial indicator against the top of the idler arm grease cap.
  6. Place a spring scale near the relay rod end of the idler arm.
  7. Important: 

       • Do not forcefully move the right tire and wheel assembly back and forth in order to cause an up and down movement of the idler arm.
            There is no control on the amount of force being applied to the idler arm.
       • Vehicle shimmy is not always caused by a loose idler arm.
            Before suspecting suspension or steering components, consider the following areas:
          - Dynamic imbalance
          - Runout
          - Force variation of tire and wheel assemblies
          - Road surface irregularities
       • Refer to Tires and Wheels and Vibration Diagnosis and Correction.

  8. Apply 110 N·m (81 lb ft) of force upward and then downward while measuring the total distance that the arm moves.
  9. Measure the total distance the idler arm moves under the applied force specified. Allow no more than 3 mm (1/8 in) deflection in each direction, for a total of 6 mm (1/4 in).
  10. Replace the idler arm if it fails this test. Refer to Idler Arm Replacement .