Bought a Denso for bank 1 and a Walker for bank 2. They are heated oxygen sensors. I did this so it would be easier to find out how much difference between brands there might be.
I replaced bank 1 with the Denso and that made things better. There was an O2 sensor code on bank 1. A few months later I put the Walker in bank 2 since there were codes for bank 2 now as well. Things didn’t get better.
With the new sensor on bank 2 it runs somewhat badly and it pings at full throttle sometimes. The pinging started when the MIL went off by itself after putting the Walker in bank 2. The check engine is off but the codes remained since I never cleared them.
With the key on and the engine cold bank 1 shows 0.3V, bank 2 0.1V, and the catalyst monitor shows 0.3V. When running the Walker on bank 2 seems to stay around 0.1V a lot more than bank 1, but it will jump up to 0.6V every once in a while.
Is the Walker sensor defective?
correction: Changed Wagner to Walker. I bought a Walker on Rockauto not Wagner.
I made a mistake in my initial post. When cold, both bank 1 and 2 sit at 0.3 Volts. The bank 1 sensor 2 catalyst monitor is at 0.1V.
I finally did this. It seemed to help a bit initially but the running poorly problem continued.
Yes and no. It had a leaking fuel pressure regulator which made it run too rich. It learned to run extra lean due to this probably before faulting the oxygen sensors, so after I fixed pressure regulator that caused the fuel being sucked in to engine vaccum problem it ran terribly since the sensors weren’t really working to correct it.
The issue is finally resolved. With the Denso in bank 2 now, I replaced the Walker with an NTK sensor. After 30 seconds, which is about how long it takes to go to closed loop, it runs great with no issues at all. When cold before 30 seconds are reached it still starts rough and loses power or misfires for about 1 second once or twice when shifting through the gears and opening the throttle. The ECU has probably learned bad data for open loop mode. I haven’t reset the ECU yet.
I wonder if the Walker sensor had a non working heater element or if it was too sensitive and would make the engine try to run too lean, or both. I suspect the ECU tunes the fuel maps based on coolant temperature, so it learned bad fuel maps from the not ready not heated sensor which it uses when the engine is cold. Or maybe it’s just more sensitive to running too lean when cold which is why it would run mostly okay when warm even with the defective Walker sensor.
One of the fuel map table’s inputs is coolant temperature. Other inputs are (depending on the design) mass airflow into the engine, ambient air temperature, intake manifold pressure, throttle position, purge valve status, learned parameters, etc. That determines the base fuel-delivery rate. I doubt the ECU uses the O2 sensor readings as inputs to the fuel maps; it uses the O2 sensors to diddle the base fuel delivery rate +/- , such that the O2 sensor reading oscillates more or less symmetrically around the lean/rich transition. When the O2 sensors aren’t working (at start-up for example) the base rate is used. The base rate will be richer on cold starts b/c the engine coolant temperature is cold then, which is an input to the table. I expect the ECU also provides some extra fuel beyond that for cold starts, being it is harder to start a cold engine than to keep it running once started. The ECU probably boosts the spark plug voltages on cold starts too.
In any event, glad your Ford is back to being a good-runner!