Catalytic converters keep failing

mayerthomas0_194215
Sun, 27 Jul 2025 22:12:58 +0000
Maintenance/Repairs

I had my catalytic converter stolen off my 1998 Toyota 4Runner (4cyl. 5 speed manual) about 4 years ago. I had an exhaust shop weld on an EPA compliant converter which lasted for about a year and a half before I got a P0420 trouble code. In that time span, Colorado (state where I am registered) regulations changed and I had to put on a CARB compliant converter. A different exhaust shop put this one on and gave me a 1 year warranty, about 3 months in the P0420 code came back. The subsequent replacement also failed within a few months, and I am now on my 4th aftermarket cat. The shop said they wouldn’t warranty them anymore, and claimed the engine was burning excessive oil, but when I checked the oil level it had burned less than a quart over 4000 miles, which I believe to be normal given the age of the car. I also ran a compression test and all cylinders were above the spec. (180-190psi). Do I just keep getting unlucky with these catalytic converters, or is something else going on that needs to be fixed? The car is in great shape and runs really well when a new converter is on, so I feel like a few bad cats shouldn’t make me replace it!

6 posts - 4 participants