Nothing has gone wrong with the car, it is an excellent car. Especially as it had not been serviced in the first 28,000 miles of its life!
This little car is a cracker! Great head and leg room. Driving position is brilliant thanks to its adjustable steering column (reach and rake), seat(height and adjustable lumbar support). The 60SX spec is just the right balance for this size of car.
Its engine is also brilliant, good acceleration, I once timed it at 9.1 seconds 0-60. It's a little noisy at high speeds but I find it just goes nicely at 90mph. It can carry 5 adults and a full boot at 107mph.
FIAT - no longer the little rust buckets they used to be!
You have a 1242cc 8 valve engine (60sx) which has 60 bhp and you timed it to 60 mph in 9.1 seconds! - eh, no. I suggest you get your speedo checked.
This is not uncommon. Many factors such as temperature of car at start and how full the tank is can easily influence the speed. This is true especially on warmer days.
I can also manage this in my '98 60s punto. The top speed is also correct, even though Fiats details say that it should be 96MPh and a 0-60 of 13 seconds! but the time is definitely true!