Manual Transaxle

Hunting (Repeated Acceleration and Deceleration) Occurs at the Set Vehicle Speed

TECHNICAL DESCRIPTION (COMMENT)
The cause is probably the malfunction of the vehicle speed sensor or incorrect vacuum in the auto-cruise control vacuum pump or actuator

TROUBLESHOOTING HINTS
- Malfunction of the vehicle speed sensor
- Malfunction of the auto-cruise control vacuum pump.
- Malfunction of the actuator
- Malfunction of the auto-cruise control-ECU.

DIAGNOSIS

Required Special Tool:
- MB991223: Harness Set




STEP 1. Check the vehicle speed sensor.
1. Remove the vehicle speed sensor and connect a 3 - 10 kohm resistor as shown in the illustration.
2. Turn the shaft of the vehicle speed sensor and check that there is voltage between terminals 2 - 3. (one turn = four pulses)

Q: Is the voltage within specifications?

YES: Go to Step 2.

NO: Replace the vehicle speed sensor. Refer to Combination Meter Assembly and Vehicle Speed Sensor. Then check that the malfunction is eliminated.

STEP 2. Check the auto-cruise vacuum pump.
1. Disconnect the vacuum hose from the auto-cruise vacuum pump and connect a vacuum gauge to the vacuum pump.
2. Disconnect the vacuum pump connector.




3. Check the auto-cruise vacuum pump and valves according to the following procedure:
- Connect the positive battery terminal to auto-cruise vacuum pump connector terminal 1, and the negative battery terminal to terminals 2, 3, and 4. Then the vacuum gauge should read 27 kPa (8.0 in Hg) or more.
- The vacuum should be maintained when terminal 4 is disconnected from the negative battery terminal while terminals 1, 2, and 3 remain connected. Then the vacuum gauge should read 0 kPa (0 in Hg) when terminal 2 is disconnected from the negative battery terminal while terminals 1, and 3 remain connected.
- The vacuum should be maintained when terminal 4 is disconnected from the negative battery terminal while terminals 1, 2, and 3 remain connected. Then the vacuum gauge should read 0 kPa (0 in Hg) when terminal 3 is disconnected from the negative battery terminal while terminals 1, and 2 remain connected.

Q: Are all of the above values satisfied?

YES: Go to Step 3.

NO: Replace the auto-cruise vacuum pump. Then that the malfunction is eliminated.




STEP 3. Check the vacuum actuator.
1. Disconnect the vacuum hose from the vacuum actuator, and then connect a hand vacuum pump to the vacuum actuator.
2. Apply a vacuum and check that the throttle lever moves and the vacuum is maintained.

Q: Is the vacuum actuator damaged?

YES: Replace the vacuum actuator. Refer to Throttle Body Assembly. Then check that the malfunction is eliminated.

NO: Check that the malfunction is eliminated. If the malfunction is eliminated, replace the auto-cruise control-ECU. Then check that the malfunction is eliminated.