E46 330ci msport coupe 2004 90k miles was running like a contented lion pulls like a train BUT started running a little rough only noticeable on idle you could only tell when stopped by the car being ever so slightly juddery engine management light on even with this prob she ran beautiful with acceleration pulled and no misfire then got worse now idles terrible and misfires when driving car very sad sat on drive :( got an engine code p1620 map cooling thermostat control circuit signal high so I changed the thermostat just incase still no change im now noticing a very serious sharp sounding clunk sounds like its coming from top right (inlet manifold side) of engine im wondering if it could be cam related camshaft intake sensor ???? but its just money money money is there any way to pinpoint this ?? me and my 9 year old boy love our beemer we gutted car is parked up she is never screwed only cruised in any help from anybody would be a godsend or any links to help diagnose once again id like to say thanks if you read and got any advise all the best kraz :)

Rather than the stat it could just be the coolant temp sensor giving a duff reading which is giving the ECU false readings. I'm only guessing at this though.