 Engine Number of Google Searches June 2018-May 2022: 567,030 Worryingly, coming out as the most common car fault are engine-related problems, which is somewhat unsurprising, given that a cars engine has so many parts that help it run optimally. Most commonly, the engine is affected by damaged spark plugs, inadequate lubrication and a failing oil ... MOT failures can be prevented by carrying out regular checks... 