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 .
    Road Test
    NOTE: It may be necessary to have the customer ride along or drive the vehicle to point out the concern. During the road test, take into consideration the customer's driving habits and the driving c ...

    Symptom Charts
    Symptom Chart - Air Leak and Wind Noise Condition Possible Sources Action Air leak around door perimeter Loose fit seal. Seal installed incorrectly. ...

    Other materials:

    Getting assistance outside the U.S. And Canada
    Before exporting your vehicle to a foreign country, contact the appropriate foreign embassy or consulate. These officials can inform you of local vehicle registration regulations and where to find unleaded fuel. If you cannot find unleaded fuel or can only ge ...

    Spark Plug - Inspection
    1. Inspect the spark plug for a bridged gap. Check for deposit build-up closing the gap between the electrodes. Deposits are caused by oil or carbon fouling. Clean the spark plug. 2. Check for oil fouling. Check for wet, black deposits on th ...

    Air Cleaner - 3.8L
    Removal and Installation 1. Remove the air cleaner outlet tube from the throttle body. For additional information, refer to Air Cleaner Outlet Pipe-3.8L in this section. 2. Disconnect the connector. 3. Remove the bolt. 4. Remove the air cleaner and d ...