OK I suppose this one is another for the Wiki. Gary: couldn't attach all the images as I was limited to 3 but please feel free to copy them and place them permanantly on the wiki link. Firstly the following explanations and part numbers are for the M52TU engine but I am sure it can also be applied to the other varients in some way. I originally experienced problems with my old 2.8 but did not initially attribute them to the camshaft sensors as the the symptoms were so intermittant. Symptoms including reluctance to start, stalling and low power but these were all occuring fairly infrequent until recently when I could repeat them after restarting the engine whilst it was luke warm. After doing some digging into the diagnostics using Carsoft I got the following error which after clearing was reconfirmed several days later when it was logged yet again after an episode of non starting, this confirmed in my mind the camshaft sensors were to blame. A trip to my local BMW dealership and I was in posession of two new camshaft sensors and new O'rings, here are the part numbers and prices; Inlet Sensor - B126.96.36.1999.165 - £70 Exhaust Sensor - B188.8.131.528.628 - £70 O'Ring - B184.108.40.2068.398 - £0.59 each (2 required) I started by removing the Exhaust sensor which is the most easy to access, the picture below shows the position and also the connector which needs removing first by pressing in the wire retaining clip and gently pulling the connector off. The sensor itself is held in position with an allen bolt underneath the socket, remove this and the sensor just pulls out. The following picture shows the new and old sensors side by side, notice how the new sensor on the right has a larger diameter which presumably is an upgrade to the original sensor fitted at manufacture. Refit the new sensor along with the new O'ring to ensure there are no oil leaks and reconnect the sensor cable. Now for the inlet sensor which is a little more tricky but still quite an easy DIY job. The following picture shows where the sensor is located buried behind the vanos solonoid. In able to access the inlet sensor the vanos solonoid has to be removed, firstly disconnect the cable at the rear of the solonoid it's a bit fidly but disconnects in the same manner as the the sensor cables. Once disconnected using a 32mm spanner slacken the solonoid off and continue to screw it off by hand, there will be a small amount of oil drip out so have a rag at hand to clean it up. The following picture shows the solonoid and also reveals the inlet sensor once the solonoid is removed. Next remove the inlet sensor in the same manner as the exhaust sensor and here comes the tricky bit. The connector for the inlet sensor is burried under the inlet manifold and removal of the airbox is required to access this, I haven't got any pictures showing removal of the airbox but all you need to do is loosen the nut on the right hand side of the airbox then unclip the air mass sensor (MAF) and seperate the MAF from the airbox, then unclip the top water hose that goes to the header tank and gently ease out the airbox from the car. This then reveals where the inlet sensor is connected which I have shown in the following picture. Remove the inlet sensor and replace with the new one again not forgetting to replace the O'ring. The following picture shows the new and old inlet sensors which again you can see how BMW have uprated the sensors. Reassemble everthing in the reverse order ensuring you do not forget to connect the vanos solonoid back up and take your car out for a test drive and feel how smooth it now runs All in all this is a relatively easy DIY job which takes around 30-45 minutes and will save people around £100 in labour if they use a dealer to do the job.