Hi there. My 2006 Diesel Jetta with 141K miles on it has suddenly started making a puttering noise. When I go around 25-35 mph, it sounds like I put a card in a bicycle wheel. Check engine light isn't on, and the temperature gauge is good. At one point it did shake slightly, but only for a second literally. It's been 6k miles since i have had my oil changed.
My car has 141000 miles.
My car has an automatic transmission.
There are a few common problems with your vehicle. The first is a problem with the EGR system. There is a pipe that cracks at a flex joint and causes a small exhaust leak, but that is normally heard all the time. The second common issue that makes a noise is a failing camshaft. The camshaft were made of too soft of a material and they wear unevenly, which in turn causes damage to the valve lifters, and can damage the valves if left too long. These are not the only possibilities, but they are common issues. I would suggest having the valve cover removed to inspect the camshaft, and checking the EGR system for leaks. If you would like to have this problem diagnosed for you, then I suggest using a qualified independent technician from YourMechanic.