he got a lemon... it was improperly fixed... but we are only hearing the side of the angry guy. no doubt that it is a horrible situation, but i'm going to do my thing of being a dick.
so lets look at this from the "suing" dealer... a car he made zero dollars on... a customer who is already irate and unable to make happy from two other dealers (at the shop they would also know that at some point, the warranty claims will start to get denied)... a fix that is not easy to diagnose... a customer who is seemingly unwilling to pay for diagnostic (in the case that it is not a warranty issue)...
running a business, you sometimes realize that if you aren't going to make a person happy, no matter what you do (in your power), then why do anything?
so while it sucks, just saying i get it.