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Mysterious Rattling

My car has recently begun to make a weird “rattling” noise. It can be heard as I accelerate (though mostly when shifting from 1st to 2nd gear, and 2nd to 3rd gear for some reason). It will occasionally be heard as I slow down to bring the car to a stop as well. Also, this “rattling” sound will be heard if I simply leave the car in neutral and tap on the accelerator. What might be causing this?

Mysterious vehicle.

This is most likely a loose heat shield on the exhaust system. While this is not dangerous, it can be really annoying. The next time that the car is on a lift for service, ask the mechanic to check for a loose heat shield. He can clamp it in order to stop the rattling noise.

The heat shield actually fell off my car about a year ago. Could this still have something to do with the problem?

Many cars have more than one heat shield, so it is possible that another one is ready to do a suicide leap. Bear in mind that the corporate bean counters at the car companies would not spend the money to put heat shields on various parts of the exhaust system unless there was a reason. I suggest that you not allow another heat shield to fall off.

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Sometimes the insides of a catalytic converter or muffler can break loose and rattle. Do this. With the car parked, lightly kick the tailpipe from the side with your shoe to get it jiggling and see if it rattles. Don’t touch it as it could be hot if the vehicle had recently run. Let us know if it rattles.

CSA

Good point, CSA!