In about 2003 lack of power diagnosed by VW dealership to be caused by carbon buildup (in manifold if I recall correctly). I recall being informed there was a small hole through the accumulation of carbon in which to take in Co2. I do not recall what the replacement part was, if any, but VW did state this issue was identified in a Technical Bulletin. This was repaired at no cost.Fast forward to 2012 and 240,000 miles later I have had absolutely no other performance or mechanical issues other than normal wear (brakes; battery; etc). However, over the last fuel tank the engine has symptoms that could be described as similar to the former carbon buildup issue. The difference being that the loss of power is minimal and intermittent and not causing any ability to effectively operate the vehicle,whereas in 2003 it was continual low power issue. It is now December and perhaps tank condensation is causing this problem (I hope). Fuel conditioner has been added after burning fuel to reserve level. 200 miles later I am still getting occasional pulses of power shortage, mostly at above 40 mph. Perhaps the conditioner/water eliminator has t obe worked through 1 or more tankfuls before all water is removed...If after this tank or perhaps 1 more tank is emptied and the problem is still there, what else might be the problem? Turbo? perhaps i should buy a Repair manual...Does any know of a free repair manual avaialble on the internet?
Intermittent and slight loss of power mostly at above 40 mph. on 2001 Volkswagen Jetta TDI