Replacing the muffler on your 2012 Honda Accord with the 2.4-liter four-cylinder engine is relatively straightforward, but getting the car up on jack stands is a bit involved. Because of the cradle width on most jack stands, you'll probably need to pad the cradles with wooden blocks to prevent damage to the body panels when supporting the car. Chock the front wheels and raise the rear, using a floor jack under the rear towing hook. Install the rear jack stands under the rear jacking points, then raise and support the front at the front jacking points. Never work under any vehicle without using jack stands.
Let the exhaust system cool completely. Using a ratchet and socket, remove the muffler heat shield, exhaust pipe heat shield and catalytic converter heat shield bolts and self-locking nuts. Discard the nuts as you will be installing new ones later. Remove the muffler tip retainer bolt, using a ratchet and socket. Slide the tip off the muffler outlet pipe.
Follow the exhaust pipe forward to the first joint flange at the catalytic converter. Apply penetrating oil to the bolts and let them soak for at least 10 minutes. Using a breaker bar, socket and wrench, remove the bolts and nuts from the flange.
Working your way towards the rear of the car, unhook the exhaust and muffler supports from their rubber isolation mounts. Support the muffler as you unhook the last mount, then lower the assembly from beneath the car.
Peel the old gasket from the catalytic converter flange and discard it. Inspect the flange for carbon deposits and clean it as necessary, using a gasket scraper and wire brush. Wipe off any remaining penetrating oil with a clean rag.
Install a new gasket in the catalytic converter flange. Raise and support the new muffler assembly, and hook it on the rubber mounts.
Install the catalytic converter flange bolts and new self-locking nuts. Using a torque wrench, socket and wrench, torque the new nuts to 25 foot-pounds. Install the catalytic converter heat shield and torque the bolts to 7.2 foot-pounds, using a torque wrench and socket.
Engage the edge of the exhaust pipe heat shield with the retainer clip, then install and torque the new self-locking nuts to 7.2 foot-pounds. Install the muffler heat shield and muffler tip, then the torque the retainer bolts to 7.2 foot-pounds. Lower the car and start the engine. Listen for evidence of an exhaust leak at the catalytic converter.
