* Check Engine Light (CEL): This is often the first indicator. The light will illuminate, and a diagnostic trouble code (DTC) related to the catalytic converter or oxygen sensors will be stored in the car's computer. Get the codes read by a mechanic or auto parts store.
* Reduced Engine Power: The catalytic converter restricts exhaust flow. If it's clogged, it can significantly reduce engine power, making the car feel sluggish and unresponsive, especially during acceleration.
* Poor Fuel Economy: A clogged catalytic converter forces the engine to work harder, resulting in lower gas mileage.
* Exhaust Smell: The exhaust may smell stronger or different than usual. You might notice a rotten egg smell (sulfur) which is a very strong indicator of a problem with the catalytic converter.
* Loud Exhaust Noise: A damaged or broken catalytic converter can cause a rattling or rumbling sound from the exhaust system, especially at higher RPMs. This is often due to internal components breaking down.
* Black or Dark Gray Exhaust Smoke: While not always indicative of a *solely* catalytic converter issue, excessive black or dark gray smoke from the exhaust could point to a problem with fuel combustion that *could* be exacerbated or caused by a clogged converter.
Important Note: Don't automatically assume it's the catalytic converter. Other problems, such as a faulty oxygen sensor, misfire, or clogged exhaust system, can cause similar symptoms. A qualified mechanic should diagnose the problem using a scan tool to read the diagnostic trouble codes and perform a visual inspection of the exhaust system. They can determine the root cause and recommend the appropriate repair. Replacing a catalytic converter is expensive, so accurate diagnosis is vital to avoid unnecessary costs.
