Hey guy's, just had used engine installed due to failure . All ok until check engine light came on. Car runs good. Ran by auto zone for a free scan and they found cat. problem (trying to plug up). When old engine blew the UIM, all the fluid came out the back. Could I just need to let the exhaust system clean it's self out by driving a few days or go ahead and have cat replaced. Thanks.

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Sony MDX-C7900 running thru Bose system-CD changer in trunk-XM-Infinity tweeters. Autolite APP 605 plugs. New left lower control arm. New water pump, ICM, Crank sensor, MAP,TPS. Working on 2nd engine. Adding to car all the time.

Cat's not the issue. It's your O2 sensors..BOTH of them. O2 sensors absolutely hate coolant, which is what they got a bath in when your engine puked in itself.

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2005 GXP - White Gold Pearl, no mods...yet.
2000 SSEi - Resurrection in progress. Built L67 w/L32 fuel rail, ported heads, and cam. Camaro front brake system, GXP cluster, and much more in planning.

Do you think the O2 sensors can be cleaned or do they get to go to heaven with the old motor?

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Sony MDX-C7900 running thru Bose system-CD changer in trunk-XM-Infinity tweeters. Autolite APP 605 plugs. New left lower control arm. New water pump, ICM, Crank sensor, MAP,TPS. Working on 2nd engine. Adding to car all the time.

Replaced. It's the only solution.

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Bye Bye:

RIP sandrock

Pull the codes first. When mine went, I only needed to replace the pre-cat sensor, since the post-cat doesn't do much but sniff the catalyzed exhaust stream and its operation isn't as critical.

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2005 GXP - White Gold Pearl, no mods...yet.
2000 SSEi - Resurrection in progress. Built L67 w/L32 fuel rail, ported heads, and cam. Camaro front brake system, GXP cluster, and much more in planning.