You can adjust ignition timing on your Jeep Wrangler by rotating the distributor a few degrees. This procedure is possible on the 4.2L engine model only though. On 2.5L and 4.0L models, the Electronic Control Unit (ECU) controls ignition timing. Before starting, make sure you have the correct timing degree and RPMs at idle specified by the vehicle manufacturer. This information is located on the Vehicle Emission Control Information (VECI) label inside the engine compartment. If the label is missing, consult your car owner’s or vehicle service manual.
Preparing for Adjustment
Timing your Jeep is best after you have driven the vehicle for about 20 minutes to make sure the engine has reached operating temperature. Park the car in a safe place and set the transmission to Park (automatic) or Neutral (manual), apply the “Parking” brakes and turn off the engine.