I have a 92 Accord DX with 420,000 miles. It burned an exhaust valve so I removed the head and got it rebuilt. After finishing the head job the check engine light came on indicating the Oxygen sensor. I replaced it with a new one but still get the check engine light blinking one blink indicating a bad Oxygen sensor. The car runs good but my mileage has dropped from 32 mpg to 26 and I cant figure out why the check engine light still indicates a bad O2 sensor. Any idea on how to figure out what the problem is?

Thanks,
CRW

 

Well, IF the sensor is known as good, then we need to move on to testing the wiring. Did the new one come with a plug or did you have to cut and splice.

There are a few other tests, the sensor (I know it is new but have to check everything). Fuel pressure, readings at the ecu.

Do you have a manual for this....the testing I'm speaking of starts ~6-24 of the service manaul I have.

 

The sensor I installed was the type you cut an splice the wires. I did check the connections with an ohm meter and the splice connections are working. I do have a Haynes manual and will do the checks they list tomorrow but there doesn't seem to be much there concerning this problem.

 

Here is a start

 

page 2

 

If you reversed the sensor wires (usually white and black), you will get a code (guess how I know?). Any chance that happened. You should have instructions w/ universal sensor to align the wiring correctly.

good luck

 

No I have rechecked the wiring to the instructions and they are correct.

 

Check the connector and wiring for faults by disconnecting at the ECU and confirming integrity of the sensor input and ground path. If these check OK, then ECU may have a circuit fault. We have seen a few of these recently for older 90-96 Accords.

You will need a shop manual to find the correct connector and wire at the ECU. Check Online Manuals post in DIY forum for a download manual if you don't have one.

good luck

 

I was just thinking there may be a problem with the ECU. I have also been having a problem with high idle around 2000 rpm after it warms up. I have replaced both the Idle Air Control valve and the Fast Idle Thermo Valve ( both used parts ) and nothing changed as far as the idle is concerned. If I unplug the Idle Air valve the rpms drop to about 700 rpms which is making me think something is signaling the valve to open up completely.

 

Possible ECU could cause high idle, but I would first adjust base idle using the idle air bypass screw near TDC on throttle body entrance. W/ IACV electrically disconnected, adjust idle speed to about 600 +/- 50 rpm.

See some recent posts on adjusting the fast idle thermo valve. From memory, remove cover and turn valve CW to barely "snug". Check for the posts.

good luck