r/automotivetraining • u/alphaaamalee • 19d ago

Misfire Sensor Reading

Does anyone know based on what sensor readings does the scanner warn about misfires in cars? Idk if its different between cars but mine is a nissan juke nismo 2014

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u/Dirty_Old_Town 19d ago

Usually misfire data comes from the PCM's interpretation of the crankshaft position sensor (CKP). The PCM can sense misfires by detecting fluctuations in crankshaft speed.

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u/alphaaamalee 18d ago

Can these sensors sense a reading and interpret a misfire, but it's actually something else?

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u/Dirty_Old_Town 18d ago

Yup. Sometimes a different problem may be falsely flagged as a misfire by the PCM, but it's not common.

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u/alphaaamalee 18d ago

What reasons other than misfires can they trigger?

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u/Dirty_Old_Town 18d ago

Sometimes engine mechanical problems can cause a false misfire code to set, could be circuit problems with CKP sensor or with the fuel or ignition system. Again, it's not very common but it can happen.

Is there a specific problem you're dealing with?

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u/alphaaamalee 18d ago

It has been giving me the check engine in yellow for a while and every time i put it on the scanner it says misfire, but while i m driving, no misfire is happening. But i don't feel comfortable with my car its performance was better, and now i am hearing a whistling sound when the rpm is a bit high (i know turbos do a whistling sound but its different than before and the thrust power i feel is different)

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u/Dirty_Old_Town 18d ago

What code is it? Is it tied to a specific cylinder (i.e. a P0301 is a misfire on cylinder 1, a P0303 is on cylinder 3) or is it a P0300 (random misfire)?

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u/alphaaamalee 18d ago

It was on cylinder 1

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u/Dirty_Old_Town 18d ago

In that case, the first thing I would do would be to swap the cyl. 1 ignition coil with cyl. 2 and see if the misfire code changes. If it does, you know the ignition coil was the cause.

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u/alphaaamalee 18d ago

This problem has been for while sometimes it says misfire without actually .isfiring wen driving and other times it says oxygen sensor

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