When is a funny noise just a noise and when is it a sign of a problem? This is an age old question that has plagued drivers since the first vehicles came off the line. If you are like most drivers, you would rather not take your vehicle in unless it really needs service.

While it is never a bad idea to get an unusual sound checked out by a trusted mechanic, there are a few specifics that are signs of trouble. If these things happen, it is best to get your car checked out by a pro:

• Pinging – If your engine pings loudly, especially under acceleration, engine trouble could be to blame.

• Knocking – Engine knocks, especially after the ignition switch has been killed, should be investigated by a mechanic in the know.

• Low-speed bucking – When a vehicle starts bucking or jerking at slow speeds, a number of issues could be to blame. Possible causes include a vacuum leak, valve malfunctions and possibly even a broken oxygen sensor.

• Stalling – When a vehicle stalls frequently, it is time to get it checked out. This could be caused by a fuel pump issue, a filter or just plain engine gunk.

When a car suddenly acts differently and does not perform as expected, a trip to the mechanic is probably in order. Bite the bullet early and a little problem might not become a big one.