* Reduced Engine Power/Performance: This is a very common symptom. A clogged converter restricts exhaust flow, leading to a loss of power and potentially rough idling.
* Check Engine Light (CEL): The CEL will almost certainly illuminate, often accompanied by diagnostic trouble codes (DTCs) related to the catalytic converter or oxygen sensors. A mechanic can read these codes to pinpoint the problem more accurately.
* Exhaust Smell: You might notice a stronger or different smell from the exhaust, possibly a rotten egg smell (sulfur) indicating a converter failure. This is due to unburned fuel passing through the converter.
* Loud Exhaust Noise: A rattling or rumbling sound from the exhaust system, especially under acceleration, can indicate internal damage to the catalytic converter. This is caused by the substrate inside breaking down.
* Poor Fuel Economy: Because the engine is working harder to push exhaust through the restricted converter, you'll likely see a decrease in fuel efficiency.
* Black or Sooty Exhaust: Excessive black smoke from the tailpipe often points to a problem with the catalytic converter (or other engine issues).
Important Note: Some of these symptoms can be caused by other problems. It's crucial to have a mechanic diagnose the issue properly using a scan tool to read the diagnostic trouble codes and perform a visual inspection of the exhaust system. Don't just assume it's the catalytic converter based on one symptom alone.
