My 99 civic D16y8 auto is getting horrific gas mileage. Ive replaced, plugs, wires, fuel filter, ran seafoam through it, etc. I had two cels one for the cat one for secondary o2, replaced both and both codes went away. Im still getting 17mpg...90 miles to a half tank.
Edit. Figured out the main issue. Will report if gas mileage is still terrible

 

Check mechanical timing, but being you had the codes I would go with a clogged / failed catalytic converter.

If mechanical timing is correct disconnect the exhaust before the cat or at least pull the O2 sensor before the cat. Put the firing order back to how it should be and try to start it.

 

I said I replaced both the cat and o2 sensor.

 

What do your plugs look like now?

 

Gonna check here soon once I make room in the garage.

 

Well I just brought car into the garage and before I pull the plugs I decided to swap the new cap on the dizzy. The dizzy is full of red death... Probably my main issue. We'll see what the gas mileage is like, now.

 

Wow, my bad. No reason to get upset. If you quickly read what you wrote it could easily be mistaken that you were talking about the O2 sensors for the catalytic converter... Anyways, the red dust usually comes from a failing bearing inside the distributor.

 

The red dust is the bearing going bad. Napa sells the bearing. You just need to press the old out and the new one in. Use electrical parts cleaner to fully clean out the inner of the distributor and sensors.

 

Wasnt trying to be an ***. Yea, I know it means a bad bearing, I have 2 spare dizzys so I just tossed on one and reset the timing.