Misfire Monitor
Misfire monitor is continuously running during engine operation. For the Misfire monitor to be enabled, the Adaptive Numerator must be learned since battery disconnect and every Key on there after (known as Power-on learning). The Adaptive Numerator is a software learning routine that tells the PCM where the crankshaft slots are. Since every crankshaft is different, the PCM must learn exactly where its particular crankshaft slots are; otherwise its RPM calculations would be wrong. After a battery disconnect and then a power-up of the PCM, the Adaptive Numerator is set to a value which it would be at if everything were perfect (crankshaft slots, sensors, PCM hardware, etc.). If the Adaptive Numerator is equal to the default value, no learning has happened and the Misfire Monitor will not run. To allow the PCM to learn the Adaptive Numerator, the following must happen:
- Open Throttle.
- Engine Cool Temp Above 100°F; Or if below 100°F, Wait For ECT Rise Of 59°F.
- More Than 10" Vacuum.
- Above 1200 RPM.
- Below 3000 RPM - A/T.
- Below 3488 RPM - M/T.