Why does the check engine light come on but the car still runs?

Answer 1

This condition is a "limp in" mode programed into your cars computer so that it still can be driven even thou a problem has been detected. In this mode the engine runs on preset program that does not require feedback from sensors on the engine to run. This "OPEN LOOP" mode does not update the computer as conditions change, therefore, performance and gas millage suffer, along with some other issues.

Have a code scan performed to see what trouble codes are stored. After locating and correcting the problem the check engine light can be reset and the engine can then run in "CLOSED LOOP". I hope my very basic answers help you to understand why you dont have to have your car towed to a repair shop !