1997 Mazda MX-5 Miata Long-Term Road Test

Edmunds.com

1997 Mazda MX-5 Miata Long-Term Road Test

Edmunds conducts a Long-Term Test of the 1997 Mazda MX-5 Miata and pulls the codes associated with a recent check engine light.

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ampim

It's most likely the cat. O2 sensors have their own diagnostic algorithms. If it was the sensor, then you'd get a sensor code. Most ECU's will intentionally change up the A/F and watch for the post-cat O2 sensor to see how much the cat cleans up the exhaust. If it's too dirty, then it'll set a code, or it might set it after a number of failed tests.

If you haven't taken it on a long (30+ min) sustained drive at highway speeds in a while, try that. The extra heat in the cat will sometime clean up the matrix of material in there and allow it to do it's job. I've had similar problems with my RX-8.

ampim

It's most likely the cat. O2 sensors have their own diagnostic algorithms. If it was the sensor, then you'd get a sensor code. Most ECU's will intentionally change up the A/F and watch for the post-cat O2 sensor to see how much the cat cleans up the exhaust. If it's too dirty, then it'll set a code, or it might set it after a number of failed tests.

If you haven't taken it on a long (30+ min) sustained drive at highway speeds in a while, try that. The extra heat in the cat will sometime clean up the matrix of material in there and allow it to do it's job. I've had similar problems with my RX-8.

deanstevenson

I thought 420 meant smoking in progress? Wait, sorry, wrong topic.