My car exhaust was rattling and making noise for quite some time. I finally fixed it, and it sounds much quieter, and even feels better.
I had particularly noticed a rattling after getting my car back from Cascade Auto after they replaced the transmission in February. However, I believe it may have been rattling to a lesser degree before then. For a while I thought it might be brake related, or worried that it might be transmission related. I checked the brakes and saw the backing plate was bent against one of the suspension arms. I bent it away, but the clearance was really narrow. The rattling reduced, but still came back occasionally.
It slowly got worse. I looked under my car at one point and saw one of the heat shields around the exhaust just after it comes off the engine was dangling and sticking out of a gap between the exhaust and skid plate. It didn’t look easy to access. I kind of worried I may have to take it to an exhaust place.
I left it go for months. It would rattle particularly at certain RPMs. When I was trying to accelerate it would go through the rattling RPM and would make it feel sluggish, perhaps because I was trying to avoid the noise. Trying to accelerate slowly and thus efficiently would particularly get caught in the rattle point.
Today I finally got around to lifting the car to have a proper look. The one dangling through the slide plate gap had been attached to a bolt through the exhaust pipe at a flange, but the connecting part had rusted away. There was also another shield right behind that one was also loose, with the bolts at the back rusted away or gone, and nothing holding it at the front. Based some thinking and some consultation with my dad, I went about securing both shields.
For the front one, there wasn’t really anything to secure it to. Luckily, it was part of an assembly of several shields that closely fit together, so I was able to maneuver it so that it was held by the others. For the rear shield, I replaced the rear bolts with some supplied by my dad. He used vice grips to get out the broken, rusted bolt. The flanges that held them were perfectly fine, luckily. We couldn’t figure out a way to actually attach the front to anything to hold it off the pipe, so I decided to fashion some stiff wire into hooks of sorts from some nearby metal brackets for the sway bar (I believe). I made two wires with one end of each wrapped around the bracket on either side of the shield, and the other end stuck between the shield and the pipe to hold them apart. I couldn’t really get a hook on that end. It seemed to work though.
It is much quieter, and driving feels smoother, most likely because I’m not trying to avoid the rattle and can just move the throttle where it should be. My gas mileage has even started moving upwards. Hopefully this all holds in place for a while at least. So far it has, with maybe a slight rattle in certain circumstances, though that could be something else.