I have an 07 plate petrol VRS (BWA engine code) with 76k on the clock. Recently it has started to run roughly when the engine is cold. At idle it is best described as a slight misfire which can be felt in the cabin. When driving it is hesitant between 1750 and 2500 rpm but clears when it gets out of this rev range. It is run on Shell fuel.

It has been to my local VAG independant garage several times for diagnosis. No fault codes were logged and real time data was within expected normal parameters on its first visit. It was suggested I run with it for a while to see if it developed further.

On its second visit it was diagnosed as the coolant temp sensor providing a different temperature to actual. Coolant temp sensor was replaced.

Symptoms remained, mpg average dropped to 26-28 mpg over mixed roads - normally bang on 34.

On the third visit it threw up a code suggesting it was the cam sensor at fault. This was replaced.

Symptoms remain.The problem is only present when cold. Once fully up to temperature there is no roughness/hesitation.

I don't want to keep throwing parts at the car whilst the garage tries to track down the problem. They appear stumped.

Any suggestions on what may be the cause? It has been suggested to me that the inlet manifold be removed for inspection of the airway, as the air inlet path behind the inlet valves could be blocked with crankcase oil/breather sludge.

Any comments or thoughts gratefully received.

check plugs and coilpack (whatever you guys call them). is the temp sensor in the intake showing the correct temperature? it might be within normal operating thresholds, but is it correct?

also yeah check the whole inlet tract and maybe give it a clean