[E90-Spartan]

Hi all,

Newbie to the forum so bare with me. I need to explain what's happened since I bought the car due to this being a returning problem!

I own a manual 2006 e91 335i with decat downpipes. I bought it around 6 months ago with 130k on the clock from a guy that works at a motorsports company building race cars, it was running ok so I thought not having owned one of these before (My Dad owns two Z3M's and a Z4 Alpina) so I'm not a complete novice with BMW's - although they are different engines, and i am some what mechanically minded...also due to the nature of the guy's trade I thought I was on to a winner.

So, a few weeks after buying it the temperature dropped due to it being Winter and it started idling rough on the morning start, (I've always warmed my cars up before driving) after pulling off and hitting around 2000rpm the car would Judder and a check engine message would appear along with reduced power. If I turned the car off and on again, let it tick over for a minute, then continue to drive everything was fine. I also took a trip to Birmingham and after that it started to Judder at low revs and make a sort of whirring sound under engine braking.

After doing some investigating I found some oil in the spark plug wells which led me to believe the rocker cover gasket had failed, I read this was common on these cars. So I stripped it down and checked over the cover itself - No holes or splits - replaced the gasket and also the spark plugs whist I had the engine cover off as I had intended to give it a service anyway. At the same time I also replaced the PCV valve with Rob Beck's up-rated valve due to reading that the OEM ones fail and can cause the said gasket to fail also - I wanted to cover all angles. Carly also threw up a Camshaft correlation code so I removed the Vanos solenoids and cleaned them out and the codes disappeared. And by this point the car has had a full service.

All seemed fine after this! Short runs, fine. Long runs, fine. Took a 4 hour round trip to Aldershot in February and put her on the dyno with my Dad's Zed club, absolutely fine, surprised me even when it ran up 316.8bhp!

But yesterday I drove down to Devon for a family holiday and all was fine until I got into the town after coming off the motorway. The car started to Judder at low revs and sounded awful at idle. Once we got to our destination I shut it off let it cool, started it up again and it was still terrible - it also came up with a warning that I needed to put a litre of oil in, I've checked and there is no sign of any leaks.

I'm at a loss now and don't know what to do. Carly hasn't thrown up anything unusual. The car has previously had the injectors replaced and I haven't had any misfire code to point to the coil packs.

I've been out today and the juddering has gone but the engine still sounds rough and louder than usual.

I hope someone can shed some light on this! Thanks in advance.