I had check engine light come on, took to Honda garage, I was told that Honda will cover any emmission problems on my car up to 150,000 miles. I have had the O2 sensor replaced, and the egr valve taken off and cleaned free of charge. My problem is that now my car has all kinds of black carbon coming out of exhaust, which I believe is the air/fuel mixture being incorrect. Hope to hear from anyone concerning my problem. Thanks

Primarily, air/fuel mixture will be controlled by the oxygen sensor and the ECM. Could the "carbon" be a mixture of water and soot? Besides the carbon, does the car run okay? Did you install an OEM oxygen sensor? I recommend Denso oxygen sensors, not Bosch or universal sensors, for Hondas.

You may want to add Shell Regane to your gas, in order to clean the intake manifold, valves, and upper cylinder head and piston of carbon. I do this every 6 months.

Why did the shop replace the o2, did the shop say it was bad. The check engine comes on there is a emission related problem. What do you mean by black carbon? HC Co Co2
I think it might be running rich, and the black smoke might be raw or unburned fuel. If the air fuel mixture is rich you will have high hc, co. If the mixture lean you will have high hc and low co.

The Honda Dealer replaced the o2 and checked the car on the machine, and it was OK, then it started getting black stuff all over back bumper, taillight,etc. I recently had the who exhuaust replaced, including the converter, but it still black bumper on a red car. My brother thought my car was running rich too, but it was OK till after the Honda dealer messed with it. Oh yes, the dealer also had to take off the EGR valve and clean out the carbon because it had part of my port block. The car seems to run fine, has plenty of power, and doesn't miss or anything.

Using a quality full-synthetic engine oil should help lessen the carbon problem you are experiencing. Sounds like the light volitile engine oil molecules are evaporating and being burned. Synthetics resist heat and oxidation much better. Use Mobil 1 5W-30. If your problem is real bad, Auto-Rx your engine first and then start using Mobil 1. You can read about Auto-Rx on the internet.

What would cause my o2 sensor 1 to read 1.95v and o2 sensor 2 .33v