I had a similar problem 2 with my tjet. I got it checked up but I don't remember exactly what was done ( it's company lease so I don't have to directly deal with FIAT service center). If I remember correctly the air filter was changed (but not sure). It's better that you get it checked. BTW, I had another issue. The power from the engine was not constant when climbing up a hill. Power was fluctuating every second even though I kept it the engine at the same rpm. I had to drive out of town on a highway with fiat service person to show him the problem. He fixed it. It was due to ill fitting air filter it seems. Just for your info .