I recently had my 2006 Jetta TDI that I've owned since brand new totalled when it was rear ended by a GMC pickup. I've experienced the same issue as you have a couple of times and found that mine was caused by the ASV or anti shudder valve. The first time I experienced that problem it was the result of installing a tuning box. Same issue and I had to pull over shut off and restart the engine for it to run normally again. The tuning box manufacturer suggested disconnecting the ASV as a fix but I chose to get rid of the tuning box instead. The most recent issue that I had with the ASV caused sluggish acceleration or the engine shutting off with a major shudder. Both resulted from the butterfly valve sticking and binding resulting from a severe carbon buildup.Car intermittently loses power and wont go past 80kmh. Rpm limited. Pull over turn it off and then on and car works as normal again.
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