What makes your montero idle rough and your check engine light go on?

Well, happy little accidents happen, my friend. A rough idle and a check engine light can be caused by a variety of things, such as a dirty air filter, a faulty oxygen sensor, or even a problem with the spark plugs. It's all just part of the journey of maintaining and caring for your vehicle. Just take it one step at a time, and remember, there are always solutions waiting to be discovered.