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I want to know if I can detect my engine is having hesitation/stumble problem from an OBD. I mean not from any fault codes, but from the parameters obtained from the OBD. e.g. calculate the obtained torque/power and compare with the power/torque demand (from OBD PID) and say if the engine is having hesitation/stumble

Soumya Sen
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  • How would you see power/torque from OBD? Stumbling and hesitation is usually felt by the driver, which is what makes him look for the problem. – I have no idea what I'm doing Dec 07 '15 at 12:48
  • Power and torque can be calculated instantaneously (using OBD parameters) and Mode 1 - 61 gives the required value link – Soumya Sen Dec 07 '15 at 13:40
  • Are you wanting to know what parameters you should monitor in real time or are you expecting to be able to read something after the fact? – JPhi1618 Dec 07 '15 at 15:21
  • @JPhi1618 Yes! I want to know the parameters I should monitor in real time and how will they vary. – Soumya Sen Dec 07 '15 at 16:58
  • Great, then you should be able to do this. Since hesitation is rarely seen as a fault (unless caused by misfires), ODB wouldn't store any data at the time. @Zaid's answer is a good start. – JPhi1618 Dec 07 '15 at 17:01

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A stumbling engine should result in abnormal engine vibrations. It should be possible to use the knock sensor(s)/misfire counter to detect abnormalities.

Note that it will not be as straightforward as setting a simple threshold-based limit since the normal sensor readout will be heavily dependent on factors like engine speed.

Zaid
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  • Thanks @Zaid . Can you tell me any possible way to do it? Any reference material? – Soumya Sen Dec 07 '15 at 17:00
  • @SoumyaSen I don't have any reference material, but I suspect that the usual signal processing techniques will be useful here - FFT, low-pass/high-pass frequency filters, online tracking of averages... You won't be able to simply code it up, some real-world testing would be necessary. – Zaid Dec 07 '15 at 17:10