NVH Diagnosis Process

Noise Vibration Harshness tests.

Slow Acceleration Test

Slowly accelerate vehicle to where the concern occurs. Record speed, RPM, and location of concern. General test to verify concern and gather more information.

Heavy Acceleration Test

Accelerate hard 0-40 mph to determine if concern is torque related.

Neutral Coast Down-speed Test

Shift into neutral and coast through speed where concern exists. Determine if concern is vehicle speed related.

Downshift Speed Test

Drive vehicle in lower gear, but at same engine speed as when you initially experienced the concern. Determine if concern is engine speed related.

Steering Input Test

Make sweeping turns in both directions. Determine if concern is due to when bearings or suspension components.

Brake Test

Accelerate to 60 mph. Lightly apply brakes to slow vehicle to 20 mph. Determine if noise or vibration is brake related.

Road Test over Bumps

Drive vehicle over rough roads or bumps. Determine if noise is coming from front, back, right, or left side of vehicle.

Neutral Engine Run Up

Idle vehicle in park or neutral. Slowly increase RPM until concern can be duplicated. Determine if concern is engine-speed related.

Drive Engine Run-Up Load Test

With brakes applied, shift vehicle into drive and increase/decrease engine RPM. Determine if cause is torque-related.

Engine Accessory Test

Remove accessory drive belts. Increase and decrease RPM. Determine if concern is engine-accessory related.

Vehicle Cold Soak Procedure

Allow engine to rest for 6-8 hour period before starting engine. Determine is concern occurs only after cold soak.