This is overlooked so often it's just silly. Especially on modern vehicles, the tendency seems to be to go after the electronics as the cause of a performance problem. Under all those electronics is an internal combustion engine of the same type we've been making since the 1930s. Check for a mechanical issue first thing if you don't have any codes stored. An engine needs to breathe. It also needs to get rid of its waste. Suck, squeeze, bang, blow: These are the steps in the combustion process. A breakdown with any link in that chain, and you get a performance problem. Listed below are a few ways to check the mechanical integrity of your engine. Don’t forget about these if your vehicle has a performance problem.