# Miata Pre-cat

**URL:** <https://community.cartalk.com/t/miata-pre-cat/59222>\
**Category:** Maintenance/Repairs\
**Tags:** catalytic-converters, mazda, miata\
**Created:** [December 28, 2010, 6:37pm UTC](https://community.cartalk.com/t/miata-pre-cat/59222 "2010-12-28T18:37:01Z")\
**Posts on this page:** 5\
**Page:** 1

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**Author:** ![Healywheelie](https://avatars.discourse-cdn.com/v4/letter/h/779978/32.png) [@Healywheelie](https://community.cartalk.com/u/Healywheelie)\
**Post date:** [December 28, 2010, 6:37pm UTC](https://community.cartalk.com/t/miata-pre-cat/59222/1 "2010-12-28T18:37:01Z")

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Can a pre-cat for a Mazda Miata ('99) be replaced by owner? My check engine light is on- runs fine. Code corresponds to “pre-cat”. Can I replace this myself?

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**Author:** ![Rod-Knox](https://avatars.discourse-cdn.com/v4/letter/r/a183cd/32.png) [@Rod-Knox](https://community.cartalk.com/u/Rod-Knox)\
**Post date:** [December 28, 2010, 6:42pm UTC](https://community.cartalk.com/t/miata-pre-cat/59222/2 "2010-12-28T18:42:17Z")

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Is that pre-cat incorporated into the exhaust manifold? If so it is fairly simple to replace if you have a good set of tools. If it is below the exhaust manifold it may require a torch.

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**Author:** ![Caddyman](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/caddyman/32/23_2.png) [@Caddyman](https://community.cartalk.com/u/Caddyman)\
**Post date:** [December 28, 2010, 7:00pm UTC](https://community.cartalk.com/t/miata-pre-cat/59222/3 "2010-12-28T19:00:54Z")

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First, replace the oxygen sensor that is responsible for throwing the code and turning on the CEL…Run a bottle of Chevron Techron through it too, clean the air-flow sensor.

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**Author:** ![Rod-Knox](https://avatars.discourse-cdn.com/v4/letter/r/a183cd/32.png) [@Rod-Knox](https://community.cartalk.com/u/Rod-Knox)\
**Post date:** [December 28, 2010, 7:07pm UTC](https://community.cartalk.com/t/miata-pre-cat/59222/4 "2010-12-28T19:07:10Z")

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Excellent suggestion Caddyman. I must have been nodding off again.

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**Author:** ![Healywheelie](https://avatars.discourse-cdn.com/v4/letter/h/779978/32.png) [@Healywheelie](https://community.cartalk.com/u/Healywheelie)\
**Post date:** [December 29, 2010, 2:54am UTC](https://community.cartalk.com/t/miata-pre-cat/59222/5 "2010-12-29T02:54:55Z")

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Thanks Caddyman and Rod!  
The car ran really rough and we replaced the oxygen sensors, ignition module and plug wires. After that, it ran smooth and corrected the problem- but then the pre-cat was damaged (as a result of the bad ignition module). We would just like to try to replace the precat if we can- we have a decent set of tools, but not a lift or anything. I think it would be hard to get under there to do any welding if required (we do have a welder).