Mini Misfire

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Mini Misfire

Postby ben.martins » Mon Dec 04, 2017 11:39 am

Hi all,

Interesting video here from the BMW Mini petrol engine. Misfire codes, poor performance and rough running are some of the problems but what conclusion would you have if you saw this capture?

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Re: Mini Misfire

Postby Liteace » Wed Dec 06, 2017 1:24 am

He could have skipped all the blar, blar, blar, life story and got straight to the point, nearly fell asleep, though I was watching a Frankie video :lol:
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Re: Mini Misfire

Postby Technician » Thu Dec 07, 2017 1:02 am

What I think you are experiencing there with the crank waveform when the misfire occurs is the slowing down of the crankshaft rotational speed. I suppose a lot depends how you set the scope, but fine tuning the operator is able to see the crankshaft slow down up to TDC and speed up after TDC, normally, and when an ignition misfire occurs, the crank will not speed up at all, hence your flat-line at the horizontal portion. It is also worth a mention that, as we had it drummed into us at college back in the 1980's, don't assume just because a part is brand new that it is not defective, always test it, which is what we were always told.

Always check the obvious!

Ask the question, why were the plugs changed!

Did the engine have a misfire before the spark plugs were changed!

Had somebody else worked on the engine before you!

Were the correct questions asked before much time was spent looking for the fault?
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