Just on AM correct? It isn't the radio or your car, it is the power lines. Many utilities read the meters remotely, they send signals via the powerlines to read meters (smart meters) and control functions at various sub stations. That is the source of your problem. The FCC is aware of it, Amateur Radio Operators have complained about it to no avail. The FCC response is to "live with it".
However, there is a way to get the attention of the FCC, contact your favorite AM station, ask for the station engineer and explain the issue. AM radio stations survive on clear signals, they pay for their licenses, when they complain, they WILL be listened too.