My 2001 C5HDI has started to blow smoke - dark colour - in the morning some times. Happens maybe once a week. Engine runs a little rough for about 2 minutes - to the end of the street - and then seems fine for the rest of the day.

No fault codes; no loss of oil; no noticeable leaks; no noticeable change to the exhaust in the rear view mirror (after the initial smoke has gone).

I am thinking that an injector might be leaking over night, and their is fuel in a cylinder in the morning . Anyone know of a GOOD injector cleaner to add to the fuel?

Any other ideas?