4.6L and 5.0L Engines
The 4.6L and 5.0L engines covered by this guide utilize a sophisticated fuel injection system in which an engine control computer utilizes information from various sensors to control idle speed and air/fuel mixtures. No periodic adjustments are either necessary or possible on these systems. If a problem is suspected, please refer to Emission Controls of this guide for more information on electronic engine controls and fuel injection.
- Place the transmission in N or P . Apply the parking brake and block the wheels. If equipped with automatic brake release, disconnect the vacuum hose and plug it.
- Bring the engine to normal operating temperature. Place the air conditioner/heater selector to the OFF position.
- Disconnect the vacuum hose at the EGR valve and plug.
- Place the fast idle adjustment on the second step of the fast idle cam. Check and/or adjust fast idle rpm to specification. Refer to the Vehicle Emission Control Information label.
- Rev the engine momentarily and repeat Step 4. Remove the plug from the EGR vacuum hose and reconnect.
- Disconnect and plug the vacuum hose at the throttle kicker and place the transmission in the idle setting position specified on the Vehicle Emission Control Information label. If adjustment is required, turn the curb idle speed screw and set the idle to the speed specified on the label.
- Put the transmission in N or P , increase the engine speed momentarily and recheck.
- Apply a slight pressure on top of the nylon nut located on the accelerator pump to take up the linkage clearance. Turn the nut on the accelerator pump rod clockwise until a clearance of 0.010 in. plus or minus 0.005 in. is obtained between the top of the accelerator pump and the pump lever.
- Turn the accelerator pump rod 1 turn counterclockwise to set the lever lash preload. Remove the plug from the throttle kicker vacuum hose and reconnect.
- Disconnect and plug the vacuum hose at the Vacuum Operated Throttle Modulator (VOTM) kicker. Connect an external vacuum source providing a minimum of 10 in. Hg to the VOTM kicker. With the transmission in the specified position, check/adjust the VOTM kicker speed.
- If adjustment is required, turn the VOTM kicker speed adjusting screw. Remove external vacuum source and reconnect VOTM kicker hose.
See Figures 1 and 2