After driving for about 30 minutes turned A/C on, 30sec later engine had misfire and keeps doing it every 30 seconds. Turn of A/C runs OK, turn A/C on again problem returns.

Returned home and tried it again when stationary and engine cuts out. Starts up straight away.

Driving to work past two weeks hasn't misfired but once it had cut out when stopped and A/C turned on.