Diagnosis By Symptom Test
- ONLY use this test procedure when directed to do so by results of Quick Tests or steps in Circuit Tests. Follow test procedures carefully.
- If engine runs rough, misfires, stalls, lacks power, or idles roughly, perform the following checks:
- Check fuel control, using Circuit TEST S, Steps 1) through 5).
- Check MAP Sensor, using Circuit TEST H, Step 11).
- Check EGR valve for correct function.
- Check ignition components (cap, rotor, wires, coil, & plugs).
- Check basic engine components (valves, cam timing, compression).
- Check for, and repair, any bad ground or power line connections.
- If there is no fast idle with A/C on, go to TEST BB
, Step 1).
- If gasoline fumes accumulate under hood, go to TEST Y
, Step 1).
- On 5.0L HO models only, if engine stumbles after hot restart, go to TEST S
, Step 14).