Grand Cherokee (4.0L) & Wrangler
The following procedure checks throttle body calibrations for correct idle conditions. To perform the following procedure, a Miller Fixed Orifice Adapter (6714) must be used. Fixed orifice adapter is a 0.185" air metering orifice. Procedure should only be used to diagnose the throttle body for conditions that may cause idle problems. Before performing this test, ensure Idle Air Control (IAC) motor is functioning properly. See CHECKING IDLE AIR CONTROL MOTOR .
- Turn ignition off. Check the throttle plate and linkage for a binding condition. The throttle linkage must be at idle position. Ensure the throttle plate is fully closed and against it's stop. Is the throttle plate and linkage free of damage? If yes, go to next step. If no, repair as necessary. Perform POWERTRAIN VERIFICATION TEST VER-5 under VERIFICATION TESTS.
- Inspect the Intake Manifold for vacuum leaks. Inspect the Power Brake Booster for any vacuum leaks. Inspect the Closed Crankcase Ventilation (CCV) system for proper operation or any vacuum leaks. See Fig 2 or Fig 3 . Were any problems found? If yes, repair vacuum leak as necessary. Perform POWERTRAIN VERIFICATION TEST VER-5 under VERIFICATION TESTS. If no, go to next step.
- Turn the ignition off. Disconnect the vacuum line at the Closed Crankcase Ventilation system fixed orifice fitting at rear of valve cover. Install Miller Fixed Orifice Adapter (6714) into the disconnected vacuum line in place of the Closed Crankcase Ventilation fixed orifice fitting. Fixed orifice adapter is a .185" air metering orifice. See Fig 1 . Disconnect the purge hose from the fitting on the throttle body. The purge hose is located on the front of the throttle body next to the MAP sensor. Cap the fitting at the throttle body after the purge hose has been disconnected. Start the engine. Ensure that all accessories are off. Allow the engine to reach operating temperature above 180°F (82°C). With the DRBIII(R), in System Tests, perform the Minimum Air Flow function. Is the engine RPM between 500 and 900? If yes, test is complete. If no, go to next step.
- Turn ignition off. Remove the Throttle Body. While holding the throttle open, spray the entire throttle body bore and the manifold side of the throttle plate with Mopar(R) Throttle Body Cleaner. Clean the IAC motor passage also. Reinstall the throttle body. Ensure Miller fixed orifice adapter is still attached to the PCV vacuum line and the purge hose fitting on the throttle body capped. Start the engine. Ensure that all accessories are off. Allow the engine to reach operating temperature above 180°F (82°C). With the DRBIII(R) in System Tests, perform the Minimum Air Flow function. Is the engine RPM between 500 and 900? If yes, repair is complete. Perform POWERTRAIN VERIFICATION TEST VER-5 under VERIFICATION TESTS. If no, replace the Throttle Body. Perform POWERTRAIN VERIFICATION TEST VER-5 under VERIFICATION TESTS.
WARNING:
Clean throttle body in a well ventilated area. Wear rubber or butyl gloves. Do not let cleaner come in contact with eyes or skin. Avoid ingesting cleaner. Wash thoroughly after using cleaner.