2004 545i engine shaking on cold start
bought this car 30 months ago when it had done 36k km.
since then, i logged up 20k. about 3 weeks ago, weather turned cold to 45-50F.
car has no problem starting in the morning, however, the engine starts to shake as if it is on 5-6 cylinders only. at the same time, engine fault icon comes on plus message warning to drive moderately or else risking overloading catalytic converter. it shook so much i had to turn off engine. strangely, engine shook far less on restart, as a matter of fact, engine was normal and responsive on the third start, there were no more warning icon and message. i could drive the car and start it several times in the same day without further trouble. diagnostic shows #2 and 3 cylinders were at fault. so i changed all ignition coils
and fuel injectors but the same problem still persists.
can anyone advice me what the problem is?