There are a handful of telltale signs your catalytic converter is on the fritz.
- Poor acceleration when stepping on the gas pedal
- Noticeably less fuel efficiency
- Dark, sooty smoke exiting your muffler
- Engine starting trouble
- Failing an emissions test
- A pungent sulfuric or rotten smell
- A Check Engine light in conjunction with any of these other symptoms
Faulty catalytic converters will often give you acceleration troubles. You step on the gas and all you feel is a jerky, inconsistent response. This is caused by a buildup of backpressure because of blockage in your exhaust. When air can’t escape, fresh air can’t come in.
An effective way to test for a blocked or plugged catalytic converter is with a vacuum gauge. By connecting the gauge to an intake vacuum on your intake manifold, throttle body, or carburetor, and recording your reading at idle, you can watch the needle as you rev the engine to increased rpm.
If all is well, you’ll see the vacuum reading stabilize.
If the vacuum reading drops, there’s a good chance backpressure is building in your exhaust system.
Overheating is another common problem with catalytic converters. Often, a failed oxygen sensor is the culprit. Oxygen sensors regulate your air-fuel mixture. When they go bad, they send incorrect information to your vehicle’s computer which can make it interpret your vehicle data as your exhaust running lean.
To compensate, your vehicle responds with a rich fuel mixture. Over time, this will clog your cat and lead to overheating, and most likely, an expensive replacement job.
If the time has come to replace your catalytic, you’ll want to check out our earlier post on choosing the right catalytic converter.