Diagnostic Method: Notes

Fig 1: Identifying Crankshaft Position Sensor Position

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When the misfire occurred, the engine speed is decreased and the crankshaft position speed will change. Calculate the interval difference value (diagnostic value) from crankshaft position speed by the following formula, and judge whether the misfire occurs or not comparing the calculated result with judgment value. Counting the number of misfire up, and if the misfire ratio is higher during 1000 rev. or 200 rev., judge NG for the corresponding cylinder.

Calculate the diagnostic value (from crankshaft position speed)

--> Misfire detection every single ignition (Compare diagnostic value with judgment value)

180° Interval Difference Method
360° Interval Difference Method
720° Interval Difference Method

--> NG judgment (Judge misfire occurrence required by the law) (Compare number of misfire with judgment)

FTP1.5 times misfire NG judgment
Catalyst damage misfire NG judgment

As the following figure, pick out a random cylinder as the standard and name it omg 0. And the former crankshaft position speed is named omg 1, the second former crankshaft position speed is named omg 2, the third is named omg 3, and the following is the same.

Fig 2: Identifying Cylinder Randomly Sequence

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