Just wanted to know if anyone could tell me what else might be my problem. My cel came on and the code was 67(low cat eff.). I put a new stock cat on and a new secondary 02 sensor on to fix the problem. But now the cel still comes on after I reset it. everything else works fine on the car. Only mod is an AEM short ram intake. Also, does code 67 affect gas mileage even with the new parts. Thanks for the help.

99 civic ex d16y8

 

Check for an exhaust leak. Are any other codes thrown? The cat is generally destroyed by the engine running rich. Have you fixed that problem?

 

no other codes, no leaks, engine's not running rich. The cel came back on within 2 weeks after replacing cat and secondary 02. Maybe the new cat was no good. Never heard of that though. It was a oem magnaflow

 

2 weeks no CEL...an engine that misfires or is running rich will kill a cat very quickly.

 

Does the code 67 have any effect on gas mileage. Thats my main concern. I get about 400+ miles to a tank now. Just wondering if I should bother with the cat if it isnt going to increase mileage anymore. I can deal with the cel being on. Plus the car runs fine. I put about 600 miles a week on it.