overfueling, ignition/valve timing out, or hopefully just air leaking through knackered exhaust gasket into pipe, all causing secondary combustion.
loose baffle
the reason you here noise from your muffler are because less pressure from your engine is going fast.
If there's a hole in the muffler, you will begin to hear a loud roaring noise when you drive. You also will notice toxic fumes coming out from the muffler. These fumes can cause headaches, dizziness, and other health problems when inhaled.
leaking or cracked manifold
A hole in the muffler would cause a knocking sound in your muffler. A loose exhaust pipe can also cause a knocking noise.
A bad muffler on a 96 civic could cause loud exhaust noise. The muffler could cause hard starting if it is stopped up.
Muffler loud noises
Sloppy timing chain?
Varies from car to car. Is it just the muffler or are the pipes a problem? Find out where the noise is coming from, check for holes, black soot or just air coming out. Be careful, it might be hot, expecially the converter & front pipe sections.
Damage. Hole. Perished gasket. Incorrectly fitted. Corrosion.
There a re number of thing that can cause it, more than likely though you'll need to get your muffler replaced, had that same problem with mine, of course my muffler had rusted off so that could also be your problem, hope this helps
A muffler is a part of a car that silences the noise of a vehicle's engine.