[arkangel643005]

Hi... sorry, forgot to post my findings on here! Basically the problem has become better lately but still not got to the bottom of it; essentially we checked the pressure of each cylinder on the car and all bar one of the cylinders were fine, but the pressure in cylinder 3 was very low (about 1/3 normal pressure), although we confirmed that there wasn't any coolant in the cylinders when we tested them so luckily this proved there isn't a problem with the cylinder head gasket - this is the cause of the misfire, once we warmed the engine and tested the pressures again, all cylinders were fine - this hasn't really been a problem for me since I know the misfire clears after about 20 seconds from cold start so I can live with that.

The problem with the engine turning over very rough appears to have been oil-related! We did have standard 10W/40 viscosity oil in it before but we did an oil / filter change and now use 5W/30 viscosity (actually this is Castrol's recommended oil type) and now the engine does turn over ok at cold start.

Basically BMW told us that there could be a number of solutions to the misfire problem but that because they would have to try so many different fixes for the problem, the labour rates would be astronomical so they advised me not to bother really! Could be anything in the cylinder head causing the pressure drop, maybe a sticking valve although I'd tried all kinds of oil and fuel additives to clear this.

So although the car does kinda run ok now, I think I could be severely tempted into trading it in at a dealership come warmer weather (when the engine seems to start with less of a misfire than in colder climates!) just in case the misfire were to become more of an issue later on. It's a shame really because the car drives great, I just don't know if I'd be prepared to continue the risk of keeping it for the long-term.