Q: Loud rattling noise

Changing an engine is a big job that involves many little details, and sometimes all of the details don’t get completely ironed out. It could be that one or more of the exhaust heat shields was not put back in place just right. It probably rattles at idle because four cylinder engines are just shakier at idle, and then they smooth out when they speed up. Try reaching under the car with the heel of your hand and banging on the exhaust system. If you hear the same sound that has you worried, then you’re on the right track. This type of issue can be difficult to diagnose, so if you need assistance, a YourMechanic certified technician can come to your location to inspect your vehicle’s rattling noise and help make any repairs.