Blue smoke means engine is consuming oil
Get compression test , probably your engine is weak and that's why it has trouble starting, valve seals maybe on the way out,
To counter a problem of oil consumption you will most likely be using a heavy weight oil which will in turn cause missing at cold starts
Also check if you have proper ground and voltage, get a grounding lot of neccessary, my mini once suffered from this missing at startup due to loose negative on body and there was a resistance to flow on start which caused improper voltage to spark plugs and misfire
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