1999 Mazda Mellenia -S, Cylinder 4 Misfire

1999 Mazda Mellenia Auto Repair Question -
Cylinder 4 Misfire

I have a strange Mazda Cylinder Misfire Question.

History 1st.2 mo ago I bought a 1999 Mazda Mellenia S with V6 2.3L engine. My wife was driving when the "check engine" light came on.

A trip to a local repair shop (a popular chain whose name I shall not mention) put the car on the diagnostic computer and it reported a "cylinder 4 misfire". They said most likely a bad spark plug or bad coil.

They took it apart and switched the cyl 4 and cyl 3 coils and put it back together. The reason given was (?) This. They said that Mazda does not give out its coil specs so that the coil couldn't be 'tested'. By switching them and doing a 2nd diagnostic, if it still showed the cyl 4 misfire it would be the spark plug. If instead cyl 3 now misfired it would mean the coil was the problem (They also said there was a small amount of oil in the cylinders indicating the seals were starting to go and although that could also cause a misfire diagnosis the fact that only ONE cyl was misfiring the oil could be ruled out as the cause. The garage said we want to be sure because they also informed me it was $300+ just for the cost of a new coil!

I was told that for the "check engine" sensor to come back on the engine would have to cool below some specified temp and then reheat to above a specified temp. In other words let the car cool overnight then drive it the next day.

NOW my question.I did exactly that and the "check engine light" never came back on. Everything now seems fine. Any idea what's going on?

Thanks Much,
Bart Hennin