INSPECTION PROCEDURE 8: Hunting (Repeated Acceleration and Deceleration) Occurs at the Set Vehicle Speed. < A/T >: Diagnosis

WARNING: This page is about a different car, the 2005 Dodge Stratus and 2005 Chrysler Sebring. However, it is still accessible from the selected car via links, so may be relevant.

Required Special Tool:

MB991502: Scan Tool (MUT-II)
MB991223: Harness Set

STEP 1. Check the vehicle speed signal.
CAUTION: To prevent damage to scan tool MB991502, always turn the ignition switch to the "LOCK" (OFF) position before connecting or disconnecting scan tool MB991502.
1. Using scan tool MB991502.
2. Connect scan tool MB991502 to the data link connector.
3. Turn the ignition switch to the "ON" position.
4. Read the MFI-DTC.
5. Turn the ignition switch to the "LOCK" (OFF) position.
Q: Is the MFI-DTC P0720 is output?

YES : For 2.4L engine, refer to Diagnosis - DIAGNOSTIC TROUBLE CODE CHART . For 3.0L engine, refer to Diagnosis - DIAGNOSTIC TROUBLE CODE CHART .

NO: Go to Step 2.

Fig 1: Connecting Scan Tool To Data Link Connector
Courtesy of DAIMLERCHRYSLER CORPORATION
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:
  1. 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.
  2. 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.
  3. 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. (Refer to AUTO-CRUISE CONTROL ). Then that the malfunction is eliminated.

Fig 2: Checking Auto-Cruise Vacuum Pump
Courtesy of DAIMLERCHRYSLER CORPORATION
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. (For 2.4L engine, refer to THROTTLE BODY ASSEMBLY ). (For 3.0L engine, 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. (Refer to AUTO-CRUISE CONTROL ). Then check that the malfunction is eliminated.

Fig 3: Checking Vacuum Actuator
Courtesy of DAIMLERCHRYSLER CORPORATION