Road Test: Notes

The following is a brief overview of each test in the order in which it appears. A review of this information helps to quickly identify the most appropriate process necessary to make a successful diagnosis. After reviewing this information, select and carry out the appropriate test(s), proceeding to the next step of this process.

• The Slow Acceleration Test is normally the first test to carry out when identifying an NVH concern, especially when a road test with the customer is not possible.
• The Heavy Acceleration Test helps to determine if the concern is torque-related.
• The Neutral Coast Down Speed Test helps to determine if the concern is vehicle speed-related.
• The Downshift Speed Test helps to determine if the concern is engine speed-related.
• The Steering Input Test helps to determine how the wheel bearings and other suspension components contribute to a vehicle speed-related concern.
• The Brake Test helps to identify vibrations or noise that are brake related.
• The Road Test Over Bumps helps isolate a noise that occurs when driving over a rough or bumpy surface.
• The Engine Run-Up Tests consist of the Neutral Run-Up Test and the Engine Load Test. These tests help to determine if the concern is engine speed-related.
• The Neutral Run-Up Test is used as a follow-up test to the Downshift Speed Test when the concern occurs at idle.
• The Engine Load Test helps to identify vibration/noise sensitive to engine load or torque. It also helps to reproduce engine speed-related concerns that cannot be duplicated when carrying out the Neutral Run-Up Test or the Neutral Coast Down Test.
• The Engine Accessory Test helps to locate faulty belts and accessories that cause engine speed related concerns.
• The Vehicle Cold Soak Procedure helps to identify concerns occurring during initial start-up and when an extended time lapse occurs between vehicle usage.