1994 Mercury Cougar

Usually a check engine means an emissions problem. What you need to do the mostly is make sure your oil is ok, your coolant is ok and brake fluid is full, more than likely you have a bad oxygen sensor. But we won't be able to tell unless you get it scanned. If you car was a 96 you could get it done for free. But its a 94 and you probably gonna have to pay for it. Thats really the only way to find out why the light is on without just buying a bunch of parts and changing stuff and spending a bunch of uneccessary money