Over the last few (actually many) months my 147 started to idle rough when stopped at lights. Then it developed a slight surge when accelerating. the surge got worse and worse to the point where low down, not a lot was happening. Only when I would get to 4,00rpm did it clear.
At the same time I began hearing loud noises from the engine bay. So loud in fact that at times people turned to see what the noise was.
So i jumped on here and started my searches. The noise i was convinced was coming from the heat shield judging from what i found on this forum site. Renowned for cracking i checked and found a crack on either side of it about half way down. I seperated the two bits to see if the noise would stop. To my dismay it did not. The noise continued and it was getting annoying. It would occur at around 2,500-3,000 rpm, nothing before and nothing after. I couldnt help but connect the noise and surging to a faulty variator.
Off it went to the dealer. I was dreading the worst.
To my utter joy the noise turned out to actually be the heat shield but it was rattling against the mount bolts of the exhaust maifoold. A few washers and noise was gone.
The surge turned out to be a dirty variator phase plunger sensor. Basically this senses the cam profile and adjusts it accordingly. Mine was stuck in an advanced stage hence the rough idle. It was merely a matter of removing, cleaning and polishing and back in.
Now she runs like a dream. Smooth as the day i got her.
Just thought i would share this in case anybody experiences the same issues.
Now i need to careful and not get a speeding ticket...