Misfire Monitoring: Notes
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Misfire detection must determine if misfire is occurring, identify specific cylinder(s) and the severity of misfire, and whether it is emissions relevant or catalyst damaging. See Fig 1. To do this, control module monitors crankshaft for acceleration losses during firing segments of each cylinder based on firing order. Process of misfire detection continues well after diagnostic drive cycle requirements have been completed. Misfire detection is ongoing and is only discontinued under certain conditions. See MISFIRE DETECTION DISABLING CONDITIONS table. See Fig 2-Fig 3 .
MISFIRE DETECTION DISABLING CONDITIONS
| Condition | Specification |
|---|---|
| Engine Speed | Less Than 512 RPM |
| Engine Load | Varying/Unstable |
| Throttle Angle | Varying/Unstable |
| Timing | Timing Retard Request Active |
| Engine Start Up | Up To 5 Seconds After Start |
| A/C | Up To .5 Seconds After A/C Activation |
| Decel Fuel Cut-Off | Active |
| Rough Road Recognition | Active |
| ASC Control | Active |