POST 1 / ORIGINAL POSTEROriginal post
Hi, How is a misfire detected? Does it notice that the RPM slightly increased just after the spark fired? thanks
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YOUR RESEARCHHow does the ECU detect misfires on 1999?
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POST 2Original post
It's usually via the crankshaft position sensor detecting changes in crankshaft speed.
POST 3Original post
Quotes source post: 16293804
I thought it sensed out of normal vibrations?
POST 4Original post
Basic answer: With OBD II, there’s no missing misfires. Most engine control systems with OBD II monitor the speed of the crankshaft between cylinder firings to detect misfires. The powertrain control module (PCM) notes the relative position of the crankshaft via the crankshaft position sensor (CKP) each time a trigger pulse is sent to the ignition system. If the crankshaft does not rotate a certain number of degrees between cylinder firings, the change in rotational velocity indicates a misfire must have occurred.
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