Hollywoodsnake

07 Civic 1.8 5 sp. Scanned it and the Upstream 02 Sensor has very low voltage to negative voltage. Down stream 02 Sensor seems to be jumping around quite a bit. Cat running about 1,000 degrees. Radiator Temp about 190, no blowing out with radiator cap off. Quite a bit of pressure when take oil cap off. No indication of fluid or oil use or discoloration. After it runs for a bit smokes on acceleration and after a while power drops and smokes excessively. Pulled plugs and none are white, all four look good. My thoughts bad Upstream 02 Sensor or bad Cat or Head gasket or Head issue. Car has 160 K miles. Engine replaced with one with 54 K miles recently. Also note Daughters Car. Did not have scanner on while driving. Heard intermittently what I interpret as a tinny sound with a nut rolling around before this started behind front wheel, where Cat is located. Codes were thrown about 3 days later. I do't know much about Honda's I have domestics.

ezone

The P0420 cat code was likely set before the sensor code, but could be caused by the sensor failing before its code set.

P0135 is a heater circuit code.

The front sensor cannot read the way you expected to see, because it is an AF sensor not an O2 sensor. It does not operate the same way an O2 sensor does.

Data list check, An AF sensor hovering right around zero is normal.
It's all liquid that is pushed out, right? No air?

What color is this smoke?

Why was this done?
What year is this current engine from?
Tackle the sensor problem first.
Then see what happens after that.

The engines don't have expected head gasket or head problems ---unless it's been severely overheated.

Hollywoodsnake

Yes just fluid pushed out no air out of Radiator. Just air from oil when cap off. Smoke looked white with slight blue cast. Wouldn't hardly run when major smoke coming out. Engine replaced because she drove car into water and got into intake, she tried to start car before pulling plugs to clear cylinders. Believe engine was out of 07.

ezone

How long ago did this happen?
If real recent, cold shock could have damaged both the sensor and the cat.


Fuel, rich, oil? Not black smoke?
Steam?
Water still in the exhaust? Has it run long enough to bake all the water out?

You wouldn't believe how long it can take.......a couple years ago I dealt with one of these where someone had filled the exhaust with a garden hose and it froze solid. It took a rosebud (torch) to get that melted enough to let the engine run, and 4 hours straight running in the shop did not get the water out, the cans were still half full of ice.
LOL it was a fun one.

---------------------------

Disconnect the front sensor and leave it disconnected.
Disconnect the battery for several minutes to clear fuel trim adaptives, then drive it and see if it runs better. I'd probably unplug the rear sensor too, just to completely disable fuel trim adaptives. If it runs normally again, I'd probably put a new front sensor in it then see how it goes.

HTH

ezone

Did the intake manifold get its water dumped out?
Did the intake system get the water dumped out?
Did the big intake chamber in the drivers fender get the water dumped out?