Cherokee 2WD L4-150 2.5L VIN H TBI (1988)
ECU - Low Idle Speed Vibration
Models
1987-1989 MJ, XJ, & YJ Body With 2.5L Engine
Subject
Low Idle Speed Vibration
Index
DRIVEABILITY
Date
March 20, 1989
No.
18-51-89
P-1187 (C18-53)
BODY CODE LEGEND
MJ - COMANCHE XJ - CHEROKEE AND WAGONEER YJ - WRANGLER
SYMPTOM/CONDITION
Some 1987-1989 Jeep vehicles equipped with the 2.5L engine may exhibit a vibration at low idle speed. This condition will be most noticeable once the
engine has reached its normal operating temperature.
This vibration condition can be improved by installing an idle speed jumper harness in the ECU circuit. This will increase the idle RPM by changing the
idle mode signal to the ECU.
DIAGNOSIS
Allow the engine to reach normal operating temperature. Connect a tachometer to the engine ignition. Set the parking brake and place the transmission in
neutral. Start the engine and verify that the engine is at idle and above a minimum of 750 RPM. Using the accelerator, raise the engine idle to 950 RPM.
If the vibration complaint is now satisfied, then proceed with the following repair procedure.
If the initial idle speed is below 750 RPM or the vibration complaint is not satisfied at 950 RPM, the cause must be determined prior to performing this
repair procedure. Determine the cause by performing a vehicle test with the DRB II or the MS 1700 Tester, and by visual inspection of components, such
as vacuum hoses and connections, powertrain mounting and exhaust system.
PARTS REQUIRED
Idle Speed Harness
1987-89 2.5L Wrangler
P/N 56002-101
1987-89 2.5L Cherokee,
P/N 83100-070
Wagoneer, Comanche
