Better Auto Sales

Jan 23, 2020 purchased a used car (2009 Mazda 6) with 81000 mileage in Better Auto Sales, Inc in LA.
Total amounted to *** including taxes, paper work, and warranty. No damage disclosed during the purchase or before selling, concluding that the vehicle is completely fine. 40 days after, March 1 2020, the vehicle had an engine problem and upon diagnostics of a licensed mechanic there is a problem with ignition cool and spark plugs and air filter which resulted to a $700 worth of repairs.
The licensed mechanic called the warranty company (AUL) that we purchased under the dealer as well and was advised that our warranty only starts 90 days after the purchase date. Thus they are not covering it.
We reach out to the dealer (Better Auto Sales) and they acknowledged that there is a ignition problem with the car and was advised that they already fixed it. However, it was never disclosed to us before purchase that there was ever a damage or an ignition problem with the vehicle which under the law they should. Also, if it was fixed, it means that it was clearly not properly fixed as 40 days after purchasing the car, we experienced the same problem.
Product_Or_Service: Mazda 6 2009