Codes 176 and 177

[rumblecloud]

176	(M) Oxygen sensor not switching - system is or was lean Left or Front HO2S - Fuel control
177	(M) Oxygen sensor not switching - system was rich Left or Front HO2S - Fuel control

I've searched thru the forum and ran across several strings that mention similar instances of contradicting codes and point to O2 sensors either being bad or not plugged into the correct connection (crossed).
RonD described symptoms he experienced, but with a different code.

Symptoms are:
Runs fine until warm.
CEL comes on.
Hard to accelerate unless you floor it

This popped up on me before when I replaced the heads and added headers. The headers had a threaded opening for an EGR connection. Since I don't have EGR, I plugged the opening with a 28mm pipe plug and some sealer. That fixed the problem until yesterday when it popped up again.

Any suggestions on what I might look for other than resealing the threaded opening -- which I will try to do tomorrow.
Is there a way to test the O2 sensors. I know "NEW" doesn't mean squat, but they have less than 100 miles on them.
Thanks in advance.
r

 

[DILLARD000]

What brand new OxSensors did you use; there's a lot of offbrand NonOEM aftermarket junk being sold?
Recommend either MotorCraft or Bosch (original maker) brands for OxSensors.
The Bosch# 15719 with 24inLong Cable+Plug will replace any Ford 4WireNarrowBand OxSensor.

 

[rumblecloud]

What brand new OxSensors did you use; there's a lot of offbrand NonOEM aftermarket junk being sold?
Recommend either MotorCraft or Bosch (original maker) brands for OxSensors.
The Bosch# 15719 with 24inLong Cable+Plug will replace any Ford 4WireNarrowBand OxSensor.

Fortunately, I used the Bosch brand from Rock.
I'll play with it some more today and clear the codes and read it again. It's not my DD or anything so there's no rush. I just like to understand what's going on and why.

Thank for the your response.
r

 

[Curious Hound]

It may not be conflicting information. Your engine might be cycling between rich and lean due to O2 sensor/circuit problem or some other issue making it LOOK like an O2 sensor issue.

 

[rumblecloud]

It may not be conflicting information. Your engine might be cycling between rich and lean due to O2 sensor/circuit problem or some other issue making it LOOK like an O2 sensor issue.

I think you are spot on. I just don't know enough yet to say what the other issues might be.
But geez....it is so typical: "It was running fine until all of a sudden this pops up...I didn't do anything to it....hahaha

thanks.

 

[19Walt93]

Don't just assume the sensor is bad "O2 sensor out of range" is not a diagnosis, it's a symptom.

 

[RonD]

Since the O2s are new, so easy to unscrew, I would swap the upstream left to right and see if the codes stay on the left(drivers side) or follows the new O2 sensor to the right side(passenger side), if so O2 is bad

Lean and rich on opposite banks can be reversed O2 plugins

Lean and rich on the same bank is something else, could be intermittent fuel injector on that bank, Clogged Cat converter IF.........that bank has its own dedicated Cat