First, your wife should be credited for keeping this from becoming a major problem.
Some spouses (M or F) would have driven the vehicle with the misfire and that would have created an even bigger problem than an incompetent or dishonest mechanic would.
I worked with a woman once who “carpooled” to work with her husband (know to be sometimes impatient and a bit of a hot head, otherwise a nice guy). They had a Chrysler minivan and one time in cold weather a rear wheel seized. He was ticked and drove it several miles to work without a single rotation.
It must be a love/hate relationship with CELs, eh?
I know what you’re saying about people going to a shop with a CEL illuminated and getting hosed, but people need oil changes, tires, etcetera, and go in and get hosed, too.
I love CELs.
They have saved me many, many times from doing a bunch of unnecessary testing and diagnostic work and have really cut to the chase and very often get one in the ballpark. Try diagnosing SRS or ABS problems, without.
I have people say to me, “I can’t work on cars, anymore because they’re all electronic with computers and much too complicated now, not like the old days.” I disagree, thanks to the OBD system.