Ford Mustang (1999-2004) Service Manual: NVH Condition and Symptom Categories

A good diagnostic process is a logical sequence of steps that lead to the identification of a causal system. Use the condition and symptom categories as follows:

• Identify the operating condition that the vehicle is exhibiting.
• Match the operating condition to the symptom.
• Verify the symptom.
• Identify which category or system could cause the symptom.
• Refer to the diagnostic symptom chart that is referred to.

Operating Condition-Vehicle is Not Moving

1. Static operation

• Noise occurs during component/system functioning. GO to Symptom Chart - Squeak and Rattle .

2. While cranking

1. Grinding or whine, differential ring gear or starter motor pinion noise. GO to Symptom Chart - Engine Noise/Vibration .

2. Rattle. Exhaust hanger, exhaust heat shield or A/C line noise. GO to Symptom Chart - Squeak and Rattle .

3. Vibration. Acceptable condition.

3. At idle

• Idle noise. GO to Symptom Chart - Idle Noise/Vibration .
• Idle vibration or shake. GO to Symptom Chart - Idle Noise/Vibration .

4. During Gear Selection

1. Vehicle parked on a steep incline. Acceptable noise.

2. Vehicle parked on a flat surface. GO to Symptom Chart - Driveline Noise/Vibration .

3. Vehicle with a manual transmission. GO to Symptom Chart - Transmission (Manual) and Transfer Case Noise/Vibration .

Operating Condition-Vehicle is Moving

1. Depends more on how the vehicle is operated

1. Speed related

• Related to vehicle speed

• Pitch increases with vehicle speed. GO to Symptom Chart - Tire Noise/Vibration .
• Noise occurs at specific vehicle speed. A high-pitched noise (whine). GO to Symptom Chart - Driveline Noise/Vibration .
• Loudness proportional to vehicle speed. Low-frequency noise at high speeds, noise and loudness increase with speed. GO to Symptom Chart - Driveline Noise/Vibration .
• A low-pitched noise (drumming). GO to Symptom Chart - Engine Noise/Vibration.
• Vibration occurs at a particular speed (mph) regardless of acceleration or deceleration. GO to Symptom Chart - Tire Noise/Vibration .
• Noise varies with wind/vehicle speed and direction. GO to Symptom Chart - Air Leak and Wind Noise .

• Related to engine speed.

• Noise varies with engine rpm. GO to Symptom Chart - Engine Noise/Vibration .
• Vibration occurs at a particular speed (mph) regardless of engine speed (rpm).

2. Acceleration

• Wide open throttle (WOT)

• Engine induced contact between components. Inspect and repair as necessary.
• Noise is continuous throughout WOT. Exhaust system or engine ground out. GO to Symptom Chart - Engine Noise/Vibration .

• Light/moderate acceleration

• Tip-in moan. Engine/exhaust noise. GO to Symptom Chart - Engine Noise/Vibration .
• Knock-type noise. GO to Symptom Chart - Engine Noise/Vibration .
• Driveline shudder. GO to Symptom Chart - Driveline Noise/Vibration .
• Engine vibration. GO to Symptom Chart - Engine Noise/Vibration .

3. Turning noise. GO to Symptom Chart -Steering Noise/Vibration .

4. Braking

• Clicking sound is signaling ABS is active. Acceptable ABS sound.
• A continuous grinding/squeal. GO to Symptom Chart - Brake Noise/Vibration .
• Brake vibration/shudder. GO to Symptom Chart - Brake Noise/Vibration .

5. Clutching

• A noise occurring during clutch operation. GO to Symptom Chart - Transmission (Manual) and Transfer Case Noise/Vibration .
• Vibration. GO to Symptom Chart - Transmission (Manual) and Transfer Case Noise/Vibration .

6. Shifting

• Noise or vibration condition related to the transmission (automatic). GO to Symptom Chart - Transmission (Automatic) Noise/Vibration .
• Noise or vibration related to the transmission (manual). GO to Symptom Chart - Transmission (Manual) and Transfer Case Noise/Vibration .

7. Engaged in four-wheel drive. GO to Symptom Chart - Transmission (Manual) and Transfer Case Noise/Vibration .

8. Cruising speeds

• Accelerator pedal vibration. GO to Symptom Chart - Engine Noise/Vibration .
• Driveline vibration. GO to Symptom Chart - Driveline Noise/Vibration .
• A shimmy or shake. GO to Symptom Chart - Tire Noise/Vibration .

9. Driving at low/medium speeds

• A wobble or shudder. GO to Symptom Chart - Tire Noise/Vibration .

2. Depends more on where the vehicle is operated

1. Bump/pothole, rough road or smooth road. GO to Symptom Chart - Suspension Noise/Vibration .

• Noise is random or intermittent occurring from road irregularities. GO to Symptom Chart - Squeak and Rattle .
• Noise or vibration changes from one road surface to another. Normal sound changes.
• Noise or vibration associated with a hard/firm ride. GO to Symptom Chart - Suspension Noise/Vibration .