Wagoneer L4-150 2.5L VIN E TBI (1990)
Powertrain Control Module: Customer Interest
ECU - Vibration At Low Idle Speed
Models
1990 MJ, XJ, YJ Bodies
Subject
Low Idle Speed Vibration - Vehicles with 2.5L Engine
Index
DRIVEABILITY
Date
April 9, 1990
No.
18-51-90
P-1056 (C18-07-0)
BODY CODE LEGEND
MJ - COMANCHE XJ - CHEROKEE/WAGONEER YJ - WRANGLER
SYMPTOM/CONDITION
Some 1990 Jeep vehicles equipped with the 2.5L engine may exhibit a vibration at low idle speed. This condition will be most noticeable after the engine
has reached its normal operating temperature.
DIAGNOSIS
1.
Allow the engine to reach normal operating temperature. Shut off engine.
2.
Connect a tachometer to the engine ignition (engine RPM may also be read using the DRB II set in the "STATE DISPLAY" mode). Set the
parking brake and place the transmission in neutral.
3.
Start the engine and verify that the engine is at idle speed of 750+/-50 RPM.
4.
If a vibration is present at 750+/-50 RPM, use the accelerator to raise the engine idle to 950+/-50 RPM. If the vibration complaint is now satisfied,
proceed with the following repair procedure.
If the initial idle speed is below the specified idle (750+/-50 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 tester and by visual
inspection of components such as vacuum hoses and connections, powertrain mounting and exhaust system.
PARTS REQUIRED
1
Idle Speed Harness
(YJ) Wrangler
PN 56002101
(XJ) Cherokee/Wagoneer & (MJ) Comanche
PN 83506388
REPAIR PROCEDURE
This procedure involves installation of an idle speed jumper harness in the ECU circuit. This will increase the idle RPM by changing the idle mode
signal to the ECU.
NOTE:
THE JUMPER HARNESS INSTALLED IN THIS PROCEDURE SHOULD BE REMOVED FROM THE EEC HARNESS PRIOR TO
TESTING THE VEHICLE WITH THE DRB II TESTER TO PREVENT INVALID TESTS.
1.
Locate the Electronic Engine Control (EEC) harness connector (A) in the engine compartment. The connector can be found on the right wheel well
near the fuel pump relay and B+ latch relay on the Cherokee, Wagoneer and Comanche models, and between the battery and charcoal canister on
Wrangler models.