Misfire Monitoring

SYSTEM DESCRIPTION
Misfire is monitored by evaluating fluctuations of the angular velocity of the crankshaft position sensor. The crankshaft position sensor allows the ECM to monitor crankshaft speed variations during each cylinder power stroke. When all cylinders of an engine are firing evenly, the crankshaft speeds up evenly with each power stroke. During a misfire, crankshaft speed decreases in that cylinder. Kia OBD-II engines use a 60 minus 2 tooth crankshaft position sensor to measure crankshaft speed and position. The ECM uses this information to determine if a misfire occurs, which cylinder it is occurring in, and the degree of misfire. If a significant misfire is detected, a DTC is stored. The MIL in the instrument panel will illuminate, informing the driver of a malfunction.

MONITORING CONDITIONS
The misfire monitoring begins as soon as 2.9 to 50 ignitions pass after engine start. It is disabled while the ECM detects a sudden change of engine speed or load. The misfire monitoring covers the full range of engine operation.

MONITORING PROCESS
A new function for pre-filtering the sensor wheel segment duration has been introduced on the Optima in order to expand the misfire monitoring range. The sensor wheel segment duration is pre-filtered by this function and then the filtered value is used to calculate the engine roughness which is compared with the reference value to detect misfiring. With this function, it is possible to eliminate the influence of the crankshaft-synchronous oscillations on the detection of misfire. These oscillations can be caused by sensor wheel tolerance or crankshaft torsional vibration. The misfire monitoring of this vehicle covers nearly the full range of engine operation in case of random or continuous misfire, and for symmetrical misfire.

MIL ILLUMINATION
The MIL is illuminated when a misfire is detected which can cause the damage of catalyst or exhaust emission higher than 1.5 times certification standard (I/M failure). The MIL flashes while a catalyst damaging misfire is being detected.

COMPREHENSIVE COMPONENTS MONITORING
Any input or output components that can affect emissions or any input or output component used to monitor any other monitored component/system is monitored. The lack of circuit continuity and rationality, and out-of-range values to ensure proper operation of the input devices, are monitored for proper response to ECM commands.

EGR SYSTEM MONITORING (EXCEPT 2.5L V6 ENGINE)
The EGR system is monitored by the measurement of manifold pressure variation by turning on EGR during coasting. The manifold pressure is measured before and after EGR valve has been activated and the corresponding pressure variation is compared with reference value to detect a EGR system malfunction.