DA40 Diamond Star
Flight Crew Multiengine; Flight Crew Flight Instructor; Flight Crew Instrument
Flight Crew Last 90 Days 40; Flight Crew Total 1150; Flight Crew Type 1150
Deviation / Discrepancy - Procedural Published Material / Policy
Human Factors
During taxi; I noticed the engine running rough and backfire. I adjusted the mixture (had leaned for taxi) and the engine ran normal. Engine run-up was normal and magneto check; indicated within published tolerances. There were no issues during the traffic pattern flight; on landing; nor during taxi to parking.  Upon shut-down; a maintenance inspector from the FAA identified himself and asked if I knew the engine was backfiring during taxi and questioned why I took off. I replied with the same answer as above.
Flight Instructor flying DA-40 aircraft reported engine running rough during taxi out due to mixture setting.