bad o2

[Christopherrr]

My left bank o2 went out and I replaced it today. Just out of curiosity, is there any performance lost with a bad o2? I didn't notice anything except for a few burps at idle. Would emulators be a better choice than getting another o2? Those jokers are expensive...

[Trash man]

O2s help control ur air/fuel mixture, they are a big part in weather to add fuel or not. performance loss? prob not much maybe 5hp at the crank

[Craig 94 TA GT]

I would assume that it would hurt power. I guess though, it would depend on what was wrong with it. From what I've learned, the PCM doesn't use O2 readings when in PE mode. However, it calculates what it should do for PE through part throttle readings...so if the O2 was throwing the A/F off under part throttle, then it should throw off the PE calculations...I think

Was it reading lean/rich, or cutting in and out?

But you have 2 O2s, and I'm not sure how each is calculated and adds to the A/F ratio.

[Injuneer]

Depends what you mean by "went out". If it just died and was producing no signal at all, the PCM stayed in "open loop" and could not adapt to changes in operating condtions, but that's no big deal, no performance loss. If it was still "working" but producing bad feedback readings, it was probably hurting performance.

You can only substitute emulators (or "sims") for the two after-cat sensors on the OBD-II cars. The after-cat sensors are only there to tell the PCM the cats are working. The PCM does not use the data to control the A/F ratio. The two pre-cat sensors must be kept, so the PCM can adjust the injector pulse widths to keep the A/F ratio where its supposed to be.

But you have 2 O2s, and I'm not sure how each is calculated and adds to the A/F ratio.

Each bank of the engine is controlled independantly, with regard to A/F ratio. Bank 1 = left bank = cylinders on the driver's side (#1, #3, #5, #7). Bank 2 = right bank = cylinders on the passenger side (#2, #4, #6, #8). The left O2 sensor tells the PCM what the A/F ratio is on the drivers side, and the PCM adjusts the pulse width of injectors #1, #3, #5, and #7. The right O2 helps the PCM to adjust the pulse width of the injectors on the passenger side.

For a little more detail, check out the "Air/Fuel Control" section of my online ScanMaster writeup:

http://members.aol.com/InjuneerZZ/ScanMast.htm

[Christopherrr]

thanks guys...yeah, injuneer, it went open loop after a few minutes. You could tell. When you cranked her, and went to idle, she would run rich and she would shake, violently sometimes (cammed almost) and after a few burps, it would settle down and run normal. So yeah, I guess it went completely out...

I should have replaced them when I did my headers...silly me. Now I know...and knowing is half the battle.