We traded in our '99 Passat a couple of months ago, and ever since then my curiosity has been burning over an issue that we never got resolved.
The car had the 1.8T engine with the tiptronic automatic. In the last three months of its life with us, we started feeling a "lurch" in the engine accompanied by a sharp drop in RPMs if we accelerated for a period of time and then took our foot off the gas...similar to what you would do if you were, say, climbing a gentle slope then reaching a red light.
The lurch tended to occur when you got the RPM's somewhere between 1800 and 2200, which made it most noticeable at low speeds (around 30-40 mph).
We took the car into the dealer, and they suspected it was worn engine mounts. The theory was that the engine was building up torque as we accelerated, and was physically rotating just a hair in the loose mounts. When you let go of the accelerator, it would kick back causing the lurch sensation in the car. Unfortunately, upon replacing the mounts, the problem did not go away (and fortunately, the dealer refunded our money, but that's another story...)
Anyway, has anyone ever experienced this? Obviously, since we don't have the car any more it's not an issue, but I am still curious as to what, exactly, might have been going on.
Cheers,
-+JLS