Odourless and poisonous carbon monoxide gas can leak from the rust holes into the passenger compartment. Tap on the muffler a, resonator, and converter gently with a rubber hammer or block of wood. Any rattles heard from inside these parts indicate an internal failure hat could lower vehicle performance by blocking the exhaust flow. The last parts to check are the exhaust pipes. Any pipes that bend easily when squeezed with a large pair of pliers require replacement.
Many newer cars have exhaust pipes made of stainless steel.
Although more expensive then regular steel pipes, the stainless pipes last much longer. Noise and smell are other indications of exhaust system problems. A hole in the exhaust system not only makes the car sound louder, but can also cause the oxygen sensor in the fuel injection system to falsely sense a lean fuel mixture. The computer then injects extra fuel into the engine to compensate and your fuel economy drops. Sometimes the extra fuel passes through the engine into the exhaust system and combines with the oxygen let in by the exhaust leak to cause a loud backfire.