Ford Mustang (1999-2004) Service Manual: Torque Converter Diagnosis

Prior to the installation of a new or remanufactured torque converter, all diagnostic procedures must be followed. This is to prevent the unnecessary installation of torque converters. Only after a complete diagnostic evaluation can the decision be made to install a new or remanufactured torque converter.

Begin with the normal diagnostic procedures as follows:

1. Preliminary inspection.

2. Know and understand the customer's concern.

3. Verify the condition - carry out the torque converter operation test.

4. Carry out diagnostic procedures.

• Carry out on-board diagnostics; refer to Diagnostics.

• Repair all non-transmission related DTCs first.
• Repair all transmission DTCs.
• Rerun on-board diagnostic to verify repair.

• Carry out Line Pressure Test. For additional information, refer to Special Testing Procedures in this section.
• Carry out Stall Speed Test. For additional information, refer to Special Testing Procedures in this section.
• Carry out Diagnostic Routines. For additional information, refer to Diagnosis By Symptom in this section.

• Use the Diagnosis by Symptom Index to locate the appropriate routine that best describes the symptom(s). The routine will list all possible components that may cause or contribute to the symptom. Check each component listed; diagnose and repair as required before changing the torque converter.

Torque Converter Operation Test

This test verifies that the torque converter clutch control system and the torque converter are operating correctly.

5. Carry out Quick Test with scan tool. For additional information, refer to the Powertrain Control/Emissions Diagnosis (PC/ED) manual. Check for DTCs.

6. Connect a tachometer to the engine.

7. Bring the engine to normal operating temperature by driving the vehicle at highway speeds for approximately 15 minutes in (D) position.

8. After normal operating temperature is reached, maintain a constant vehicle speed of about 80 km/h (50 mph) and tap brake pedal with the left foot.

9. Engine rpm should increase when brake pedal is tapped, and decrease about five seconds after pedal is released. If this does not occur, see torque converter operation concerns. For additional information, refer to Diagnosis By Symptom in this section.

10. If the vehicle stalls in (D) or manual 2 at idle with vehicle at a stop, move the transmission range selector lever to manual 1 position. If the vehicle stalls, see torque converter operation concerns. For additional information, refer to Diagnosis By Symptom in this section. If the vehicle does not stall in (D), refer to Diagnosis By Symptom in this section.

11. If the vehicle exhibits a vibration during the road test, complete the Road Test Evaluation Form.

This form will aid the technician in determining the source of the vibration.

NOTE: The following is a list of common vehicle concerns that have been misdiagnosed as torque converter clutch shudder. For diagnosis of the following items refer to the appropriate sections of the workshop manual and the Powertrain Control/Emissions Diagnosis (PC/ED) manual.

• spark plugs - check for cracks, high resistance or broken insulators
• plug wires
• fuel injector - filter may be plugged
• fuel contamination - poor engine performance
• EGR valve - valve may let in too much exhaust gas and cause engine to run lean
• vacuum leak - engine will not get correct air/fuel mixture
• MAP/MAF sensor - incorrect air/fuel mixture
•  HO2S sensor - too rich/lean air/fuel mixture
•  fuel pressure - may be too low
•  engine mounts - loose/damaged mounts can cause vibration concerns
•  axle joints - check for vibration

Visual Inspection

This inspection will identify modifications or additions to the vehicle operating system that may affect diagnosis. Inspect the vehicle for non-Ford factory add-on devices such as:

• electronic add-on items:

• air conditioning
• generator (alternator)
• engine turbo
• cellular telephone
• cruise control
• CB radio
• linear booster
• backup alarm signal
• computer

• Vehicle modification:

These items, if not installed correctly, will affect the powertrain control module (PCM), or transmission function. Pay particular attention to add-on wiring splices in the PCM harness or transmission wiring harness, abnormal tire size, or axle ratio changes.

• Leaks; refer to Leak Inspection.
• Correct linkage adjustments; refer to Section.

Shift Linkage Check

Check for a misadjustment in shift linkage by matching the detents in the transmission range selector lever with those of the manual lever in the transmission. If they match, the misadjustment is in the indicator. Do not adjust the shift linkage.

Hydraulic leakage at the manual control valve can cause delay in engagements and/or slipping while operating if the linkage is not correctly adjusted. Refer to Section  for shift linkage adjustment.

Check TSBs and OASIS

Refer to all technical service bulletins (TSB) and OASIS messages which pertain to the transmission concern and follow the procedure as described.

Carry Out On-Board Diagnostics (KOEO, KOER)

After a road test, with the vehicle warm and before disconnecting any connectors, carry out the Quick Test using the scan tool. Refer to the Powertrain Control/Emissions Diagnosis (PC/ED) manual.