O2 sensor proper voltage output

[Srgould41]

I have a '96 Contour with a 2 liter motor and about 130k on it. I have been getting OBDII code 171 (bank 1 too lean). I replaced both O2 sensors (third time), but the code came back. I have an adapter and software to monitor the car's computer on my latop so I hooked it up. The front sensor I replaced was not in spec so I bought a better one. That one has good readings now.

Now I wonder about the rear. It reads 1.275 volts continuous (extreme rich). All my previous Google research shows 1.1v being about the max output.

Has anyone monitored their O2 sensors and know what the rear sensor should be reading out? I have not found any other valid references to what could be causing the 171 code other than O2 sensors so I am kind of at a loss as to what is causing the issue.

Steve

 

[projectSHO89]

O2 sensors don't cause "lean" codes.

A "lean" code means the PCM has enriched the fuel trim to it's maximum limit but the A/F is still shown in the "lean" zone.

Generally, these codes are cause by un-metered air into the intake, misreported air mass, insufficient fuel supply, or an exhaust leak adjacent to the O2 sensor that skews the sensor's readings. Pull your freeze-frame data to see the conditions under which the fault has occurred.

 

[Srgould41]

Thank you for your response. Every article I have read so far has said to replace the O2 sensors. I got rid of that error in the past by doing so, but not this time.

I'll look into the air inlet and exhaust for issues. I replaced the MAS a year ago when it had failed. Maybe I'll get lucky and find a big crack in the exhaust manifold

This weekend i hope to drive around a bit (my wife driving) while I monitor the data. I'm not sure if my application can save the data, but I'll check.

 

[Srgould41]

Edit: Starting new thread.

So here is an update. I looked all over the engine and don't see any visual issues. I changed the fuel filter. Draining it produced some metal flakes, plastic pieces (not much of either) and a bit of water.

I hooked up a vacuum gauge and at idle it reads between 13 and 17 inHg. Very low in my opinion, but I don't know what it should read. The vacuum was steady , only pulsing as idle speed changed. I looked around some more, but I don't see any obvious signs of a leak. I sprayed carb cleaner at all the likely spots, but no change in idle.

I would like to test the fuel pressure, but my software won't test, only read. i think I can get a gauge from the local parts store for testing. Is there a way of getting full fuel pressure without a test program?

Steve