10. Porsche 996
In 1998, the 996 generation of the 911 debuted, shocking Porsche purists. Air cooling, a defining characteristic of the car, was gone. The reason was that air cooling couldn’t handle the rising power of modern engines as well as the demanding engineering of Porsche cars. The engines had to use regular water cooling, which is far more efficient and commonly-used. Some experts say that removing air cooling caused the 911s to lose some of their appeal. However, it was the right move because it enabled the engineers to develop the car.
However, the biggest problem wasn’t the engineering or design. Rather, it was one tiny yet crucial mechanical component called IMS for “intermediate shaft bearing.” It is a small shaft that connects the crankshaft to the camshaft. Porsche never provided the proper lubrication, causing the bearings to break, which led to fatal engine failure. The absolute worst thing is that IMS could fail without any warning since it wasn’t connected to normal wear and tear or total mileage. If the IMS fails, drivers have to do a full engine rebuild, which is expensive and frustrating.