Air/fuel ratio imbalance

[Derekb]

I thought I fixed the check engine light on our 2017 chassis F-53. I found the oxygen sensor wire (front passenger side) touching the exhaust. I’m pretty sure it only melted one wire insulation. I taped up the wires and put the harness back in the holder. Check engine light went out.
Now, we took a one hour trip. Check engine light came back on. My code reader says air fuel ratio imbalance.
Any ideas? 19,740 miles.

[ArtJoyce]

You are either running to lean or rich. You are outside of the threshold for the engine normal automatic adjustment range. The primary thing adjusted are the injectors open duration and when open in relationship to TDC. I would clean the Air Flow Sensor and add some injector cleaner. There is an air sensor cleaner you can buy. Be carful when you clean it there are very thin wires that you can break.

[Flyer15015]

Since and oxygen sensor uses "resistance" to send it's info to the PCM, you may have altered the value of the signal with your "Fix".
Were it mine, I would replace the O2 sensor AND the wire attached.
No big deal, as it just plugs in to the harness.

What code did your reader throw ?


Mike in Colorado

[HarryStone]

Originally Posted by Derekb

I thought I fixed the check engine light on our 2017 chassis F-53. I found the oxygen sensor wire (front passenger side) touching the exhaust. I’m pretty sure it only melted one wire insulation. I taped up the wires and put the harness back in the holder. Check engine light went out.
Now, we took a one hour trip. Check engine light came back on. My code reader says air fuel ratio imbalance.
Any ideas? 19,740 miles.

Your code is likely tied to the front O2 sensor. It is the one that 'looks at' the air fuel mix in the exhaust, if it senses too much unburnt fuel, it will first try to lean the mix via the computer, and it that is unsuccessful, then it will set the code. Replace the sensor, as the wires play a significant role in the resistance of the system.

[Derekb]

Thanks all for the prompt replies. I made it home, another 1 hour journey. Engine light is still on and it has just a little “stumble” under load.
My miserly self thought that the O2 sensor was just grounding out due to the bare wire on the exhaust. I understand it is resistance oriented. I only taped the wire, did not splice or in any way I can think of change it’s resistance.
But, I will replace that sensor and check the air flow sensor and see if I can avoid seeking professional help!

[Flyer15015]

Derek,
You know that it "usually" takes a special split socket to remove a sensor, due to the size of the plug at the end of the wire, You cannot slip a regular socket or a box end wrench over the pig tail.
Harbor Frt has them if you don't want to go to Sears.
Don't try to remove the sensor with an open end wrench or a Cresent.
And just for grins, you know that there are 2 of them on the exhaust pipe.
You might want to consider replacing both......
CRC make a good MAF cleaner. Please do not use anything else, as they leave a residue and that is not good.
Just saying...........

Mike in Colorado

[tderonne]

What code? P219A?

An imbalance code is not a rich/lean type code. It's meant to find problems with individual cylinders. The O2 sensor (which is not a resistance type of sensor - it generates a voltage) data is used to adjust the fueling in the bank it's in. If one cylinder is running lean, it can only add fuel to the whole bank. An imbalance code doesn't tell you which cylinder(s) is(are) the issue, just that there is an issue.

You'd normally be looking for leaks or issues with individual cylinders, but since you know you have harness issues, I'd start there, make sure that's not causing further issues.

[Derekb]

Flyer and tderonne,

Thanks.
I did get the O2 sensor off today with a 7/8' wrench. I soaked it with Kroil first for a few hours. I did pick up the special O2 socket but I'm not sure I will need it.

I spoke to my mechanic/friend today for a good length. He mentioned a few other possibilities. He did not think the O2 sensor would be damaged by grounding out on the exhaust.

He suggested checking the chassis fuse box to see if any fuses were blown by the grounding of the O2 sensor. He also suggested clearing the codes and checking if that made any difference. I think my cheap OBD dongle and iPhone app will do this. I will try tomorrow. If my app does not work he offered to make a house call to clear the codes!

I did pick up a new O2 sensor today at NAPA. Of course they ordered the wrong (shorter wire driver's side) sensor. They are reordering the correct one now and will exchange. I really don't think with less than 20K the O2 sensors should need to be replaced.

And yes, currently code P219A. Originally it was an "O2 sensor right bank" I think.....

So the saga continues.....of course!

[Arch Hoagland]

Have you ever cleaned your MAF?

[Derekb]

Today’s report:

Cleaned MAF
Checked O2 fuse (#3), fine
Reinstalled slightly melted wire O2 sensor (I will pick up new one Monday)
Cleared the codes with my little gadget that plugs into OBD port and connects to phone

Started it up and,,,,,Fine! No light. Sounds smooth.
But, need to go for a test drive to put some load on it and see if it’s really ok now.

[Arch Hoagland]

Keep us posted.....