I had a friend who mod’ed a Corcair to an unbeatable autocross car with him behind the wheel. This was in the 80s. The other drivers never saw it coming.
I wouldn't call it a FAILURE, but it sure weren't no "sport coupe". My '74 T-bird (otherwise known as "the pimp-mobile". 460 4-bbl, 5,300 pounds, EIGHT MPG. But boy was she smooooooth.
The Mustang II front end changed drag racing. So much so that they still actively swap in Mustang II front ends and steering racks today. It wasn't that big of a failure.
80's Ford Escort I remember it had some primitive computer that controlled the carburetor. Left me stranded at the worst time.
Get this; the dealership was over an hour away and I had just got it out of the shop when on the way home it just quit accelerating going up a hill of all things. It just idled no matter how far the gas pedal was pressed. I pulled it to the side of a 2 lane county highway and discovered the carbs linkage cable was off. Luckily it wasn't broke but just popped out of a slotted fitting. That was the last straw that broke the camel's back, it had to go and good riddance.