Idle speed is not adjustable. If engine idle is not 730-830 RPM, check for contaminated fuel, vacuum leaks and correct ignition timing. Ensure throttle bore, EGR system and PCV system are clean. If these are okay, see TESTS W/CODES - EEC-IV (4.6L) article in the ENGINE PERFORMANCE section for additional procedures.
Note. If electric cooling fan comes on, discontinue testing until fan goes off.
Scheme 2
5.0L
- Disconnect negative battery cable for at least 5 minutes and then reconnect it. Start engine and allow to idle for 2 minutes. Snap throttle open and then return it to idle.
- Lightly depress and release accelerator. If engine idle speed is correct, adjustment is not required. If engine idle speed is not correct, turn ignition off. Install a 0.025" feeler gauge between throttle plate stop screw and throttle lever. (Scheme 2)
- Place transmission in Park (A/T) or Neutral (M/T), and apply parking brake. Start engine. Raise engine speed to 2500 RPM for 30 seconds and then return it to idle. If idle speed is less than 625 RPM, go to next step. If idle speed is greater than 725 RPM, go to step 5).
- Turn ignition off. Check throttle body for throttle plate orifice plug. (Scheme 3) If there is no plug, turn idle adjusting screw clockwise to adjust idle speed. If there is a plug, remove it and turn screw to obtain correct idle speed. See IDLE SPEED SPECIFICATIONS table. After adjustment, ensure screw is in contact with lever pad.
- Turn ignition off. Disconnect air cleaner hose. Using tape, block off orifice in throttle plate. If orifice is already plugged, go to step 8). On mass airflow engines, connect air cleaner hose. Start engine and check idle speed.
- If engine stalls, crack throttle plate open using throttle plate stop screw. (Scheme 2) If idle speed drops to specification or less, or if engine stalls, turn ignition off. Remove air cleaner hose. Remove tape covering throttle plate orifice.
- Select correct color plug for orifice. Plugs are available in Throttle Plate Plug Kit (FOPZ-9F652-A). Reconnect air cleaner hose, and start engine. Recheck idle speed. If idle speed is not within specification, turn adjusting screw clockwise to obtain correct idle speed. See IDLE SPEED SPECIFICATIONS table.
- Remove feeler gauge. Turn engine off. Disconnect battery for 10 minutes. Perform KOEO self-test to ensure trouble codes are not in PCM memory. Start engine, and allow idle to stabilize for 2 minutes. Snap throttle open and then return it to idle.
- With engine idling, lightly depress and release accelerator. Perform KOEO self-test, and service codes if present. On models with automatic overdrive transmission, check throttle valve pressure adjustment.
