New O2 Sensor-Slow Response

[ron96ltd]

Well, I've replaced the passenger side O2 Sensor, gone back to Autozone to clear the CEL and found that the driver's side O2 sensor now tests bad and the new one tests "slow response". Autozone says that the computer hasn't adjusted to the new sensor yet. Anyone else got an opinion of what's going on. Yes, I bought another O2S for the driver's side.

Ron
96LTD

 

[88vert]

Did you reset the trucks computer?

 

[ron96ltd]

Yes, I reset it at Autozone. The CEL was out for 20 mins or so then came back on. I went back to Autozone and found that the new O2S tested slow response.

Ron
96LDT

 

[MrShorty]

On the older explorers, there are two kinds of computer resets (and I think it's still the same on the newer ones, correct me if I'm wrong). The one you did at Autozone probably just clears the old trouble codes out of the computers memory, but leaves intact the old "adjustment" factors that the computer calculates as the vehicle wears to account for the wear. This latter reset requires disconnecting the battery for several minutes. You then drive the vehicle to allow the vehicle to relearn the wear state of the vehicle. Easy way to be sure that this isn't the problem

 

[ron96ltd]

I understood that I was supposed to disconnect the battery while replacing the O2Sensor. This afternoon when I replace the driver's side sensor I will again disconnect the battery. Are You saying that after Autozone clears the codes, I should disconnect the battery again for 5-10 minutes?

Thanks for the help.

Ron
96LTD

 

[Robert]

Did Autozone actually monitor the O2 sensors and watch their response? The Ford specification is that the HEGO should go from rich to lean, or from lean to rich at least once every 3 seconds. The HEGO voltage should toggle above and below .450 DCV and should never go negative. Normal range is from .050 to .900 VDC.

 

[ron96ltd]

No. They just downloaded the codes, determined what they were, then had me clear the codes with their electronic monitor. At that point the CEL was out. I then drove the car for 15-20 mins and the CEL returned. I then went back to Autozone where they again downloaded the codes and determined that the new sensor was responding too slow.

Ron
96LTD

 

[Robert]

I am assuming you have been replacing the upstream sensors? Is yours the V8 or 4.0L OHV? Are you sure you even have the right O2 sensor? If you have the V8 then you have 4 sensors, two before the cats and two after. If you have the 4.0L then you have 3, two before the cats and one after. If the code was for the downsteam O2 sensor(s) reacting too slowly, it's possible that you aren't replacing the right sensor or the problem may be in your catalytic converter. In other words if the code was for a downstream sensor and you are replacing the upstream sensors, it isn't going to help. What was the actual code number they pulled? At $50 an O2 sensor, it could get expensive if you end up replacing all 3 (4) and have a completely different problem.

 

[Rhett]

You have to replace O2S in PAIRS--each O2S has its counterpart. Never just 1 at a time, else your readings will be off and CEL may remain.

 

[ron96ltd]

Yes, these are the upstream sensors and this is the 6 Cyl truck. The codes have all been for the upstream sensors, except that after the new O2S was installed, there was a time when the fuel mix was rich and it triggered the downstream sensor. After clearing it, it never came back, so all seems well there. Thanks for asking.

What are the chances it is a faulty sensor?

Ron

96LTD

 

[Robert]

Originally posted by ron96ltd
. . .
What are the chances it is a faulty sensor?

Not likely, especially if they were a reputable brand such as Bosch.

 

[ron96ltd]

Interesting situation today. Last night I attempted to replace the driver's side O2S, but was unable to get the electrical connector disconnected. Finally gave up. In the mean time, I had the battery disconnected (probably 2 hrs). This morning I drove 30 miles and no CEL. How about that!! We'll see if it lasts.

Ron

96LTD