I have a 2002 Honda Civic 1.7L (all stock). It just started missing and smokes on startup. Smells very rich, looses speed while cruising and misses a little while accelerating but will clear out over 3/4 throttle. Scanned it and came up with P0301, P0302, P0303, P0304, P1457, P0300 and repeats of these... I was looking under hood and noticed exhaust manifold is cracked right about O2 sensor (unrelated???). Wondering if there are any ideas on where to start first? It's a 4 separate coil pack ignition system. Help???

 

The manifold could be the cause of the issues, as your fueling is based off of how much fuel the secondary O2 sensor reads.

 

Have you removed the spark plugs and looked at them? When was the last time they were changed?

I thought the fueling trim is based on the primary O2 sensor readings. Still a valid thought, but the O2 won't make it so rich that it misses.

When was a valve adjustment last done on this car? Is the air filter clogged?