Hi,

I have a 2003 S-type 2.5l, 150,000km. When cold starting, the engine starts fine and the rpm is around 1,500rpm. After a few seconds, when the rpm starts to drop, the engine starts to run very rough, and the engine light starts to come on, sometimes flashing. After a few more seconds, when the rpm reaches around 1,000rpm, the engine runs fine again, which it then continues to do while driving. The error code is ''misfire cylinder 1 -3 -5''. I suspected that it could be a vacuum leak, and replaced all the gaskets on the intake. I also replaced the plugs and coils, but none of this has helped. Does anyone have an idea what could be wrong?

I'd read the DTCs first before you fire the parts cannon at it. It sounds like the whole bank is effected so i'd look more at a fuel delivery/pressure problem on that bank and as a general bit of maintenance, run some injector cleaner through it.