Thread: Regrounding the O2 Sensor

Not a bad idea to reset the ECU.

^How what you go about doing this? Unplug the engine harness from the ECU, or just leave the battery cables off over night and plug them back up in the morning?

Negative battery cable off for at least 30 minutes.

I did reset the ECU and the difference in driveability was quite huge for what I replaced. It is comparable going from a bad ignition to a proper one.

Of course you really should have better mileage but if you will notice that, maybe not. I got 20% increase but after the ECU had learned that 20% increase became closer to 10% increase which puzzles me. I still have not so great sensors on the engine, dunno how that would relate, but you never know what the ECU will do with that

So probably the lesser the increase in mileage the lesser you will notice in better driveability. It also depends on the state of related sensors like MAF/temp. I suspect CAS too.

But, you do have a fast heating O2 now so short city driving with cold engine definately should be better. Maybe other ppl can tell you how much to expect.

Btw, I know for sure my O2 sensor was in pretty bad shape, not much hysteresis, rather running in circles. I'm not exaggerating that WOT in 2nd gear made so much fume (not very warm engine and cold winter weather) in the rear window a whole car could dissapear behind that. Had also to do with the thermostat.

I also noticed something I already knew, engine misfired a bit. Today I replaced dizzy and cap expecting it would go away (whole ignition replaced besides CAS sensor) So with the new lambda and the old dizzy and cap, driving 1700 rpm in 5th gear made audible it was misfiring when driving while I couldn't hear that before the new lambda/O2 I mean.

This for giving you an impression what to look for.

richardwbb, thank you for a fine and educated post. You are the second person I know that went into that detail, besides DC Scotty

The whole 20% increase going to 10% doesn't surprise me, especially on OBDII. I would see the same results NA, I would get great gas mileage but then ECU would reduce it back down. It could be because you were running leaner and it tunes it self to be back to stoich?

The new Plano(sp?) type Oxygen sensors do indeed heat up faster, thus it starts getting a more accurate reading quicker then the Thimble type.

IDKFRLPT

Ok after the BOSCH #15727 install, my gas mileage didn't get much better, but I had a few problems still at hand that I recently fixed. I still need a front end alignment, but the things I made adjustments to should help. I'll be filling up soon and report back with more updates.

1.) I adjusted the tire pressure on all 4 tires
2.) I fixed the rear driver side sticky caliper.
3.) Full coolant system/block flush.
4.) ECU reset.
5.) Fresh oil change.

Well, from personal experience, it doesnt fry the ECU, it blows a fuse inside the car.

I was crying when I thought I fried my Calum RT after making the idiocy of grounding the 12V wire of the MAF. Luckily it was only the fuse...

Do you splice this into the o2 sensor plug or do you splice it into the harness?

O2 plug! It's easier to get a new one if you screw it up. When replacing the O2 sensor, just cut the wires, and recrimp.