Q: Motor replaced in 04 honda, rough idle, worse with AC what could it be!. on 2004 Honda Civic

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We had the motor replaced just barely, and it kicked on the check engine light kicked on, and got a code read and it says that it was a exhaust deficiency or something somewhere, how do we tell what it is and what to replace? It does it whenever it's on, it vibrates B's jfmthe time. worse with the ac on, think the code we got for it doesn't
(1) Answer
Hello, you appear to be flying totally blind here with a lot of generalities. Even so, with just replacing the engine, it could be darn near anything. Have a qualified technician with proper equipment and training and manuals check out your concern. Good luck.