BMW Repair: Engine cut out, oil filler cap, bmw 318i

Question
my 2001 BMW 318i has started to cut out when coasting but only when the air conditioning is on. there have been no problems with it up to now. No warning lights or faults are visible

Answer
Ian, we don't have E46 318i in the U.S.
I would look toward a malfunctioning idle valve if the car has some miles on it. Remove the belts and check the Compressor for smooth movement turning by hand. Also check other belt driven components while you have the belts off. Also check the PCV valve. Slightly crack open the oil filler cap with the engine idleing. Should feel a little vacuum and a slight change in RPM. Valve is faulty if there is a lot of vacuum and a strange honking noise when doing this. Just some things to look for. Is your four cylinder an M44 1.9liter? Like I said we don't have em here.
-Evan