ECM - Engine Vibration At Idle

91amcjeep02

NO.: 18-52-91

GROUP: DRIVEABILITY

DATE: Mar. 11, 1991


SUBJECT:
Engine Vibration at Idle 2.5L Engine


MODELS:
1991 (YJ) WRANGLER


SYMPTOM/CONDITION:

Some vehicles equipped with the 2.5L engine may exhibit a vibration at idle speed. This condition will be most noticeable after the engine has reached its normal operating temperature.


DIAGNOSIS:

1. With the vehicle's parking brake set and the transmission in neutral, allow the engine to reach normal operating temperature. Shut off engine.

2. Connect a DRB II tester to vehicle. Start engine and using the DRB II, verify that engine idle speed is 750+/-50 RPM in neutral.

3. If a vibration is present at 750+/-50 RPM, use the accelerator pedal to raise the engine speed to 850 RPM. If the vibration complaint is now satisfied, proceed with the following repair procedure.

If the vibration complaint is not satisfied, the cause must be determined prior to performing this procedure. Determine the cause by performing a vehicle test with the DRB II and by visual inspection of components such as vacuum hoses and connections, powertrain mounting and exhaust system.


PARTS REQUIRED:

1 Wiring Harness Jumper PN 4638313

Figure 1:

REPAIR PROCEDURE:

This repair involves the installation of a wiring harness jumper assembly.

1. Be sure that the ignition switch is in the OFF position.

2. Locate the 6-way pigtail connector adjacent to the SBEC and taped to the main bulkhead wiring harness (Figure 1).


3. Remove the cap from the pigtail connector and install the wiring harness jumper, PN 4638313.

4. Start the engine and verify that idle speed is now 850+/-50 RPM.


POLICY: Reimbursable within the provisions of the warranty.


TIME ALLOWANCE:
Labor Operation No. 08-90-65-95 . . . . . . . . . . . . . . . . . 0.3 Hrs.


FAILURE CODE: PI - Poor Idle