Tim Benton

iTrader: (1)

Although my sensor (napa) probably doesn't have 12K on it, it is right up close to the curve in the DP. I think the exhaust flow has impaired it since lately at various times, when I let off the throttle in 4th gear, the O2 number would drop to .01 to .03 as the injector cycle drops to 0. After driving the car hard with some 4th gear top end runs, the same test as before resulted in .15 to.17 as the lowest number the O2 would go. Even after driving normally for the next 30 mins, hardly no boost, it still would not drop lower than .15, and would go over 1.10 or so when given moderate throttle. I'm going to get another one and see what it shows. I'd hate to be running lean now since if my O2 sensor was screwed up and scewed upwards, that I was trying to pull fuel out thinking I was running rich, when I was actually running close to lean.

Anyone else notice this with their stock o2 sensor? Check it and see what O2 voltage you get when you lift off the throttle in 4th gear...before really driving it hard. then drive it hard, some good boost going in 3rd and 4th gear, and see what it shows then. I know heat can affect the number but, damn thats alot.

Tim Benton

atihun

In the middle and upper ranges where it matters, your O2 readings will not skew (add or remove) fuel from the system. At that point it is all from the map, no?

As far as tuning with the stock O2 sensor, it is only good for a rough estimate.

I did not notice any different readings when I changed my stock O2 sensor at 85k with another stock sensor. I now have 95k and it still has very similar readings.

I will try to remember and take a look at the readings before and after.

~Attila~

rynberg

Any non-heated O2 sensor is not accurate until warmed up. Also, I believe Atihun is right, the car only uses O2 readings when idling or in cruising situations, not WOT or heavy load situations. The stock O2 sensor is not accurate at those loads, which is why the computer resorts to built-in maps instead of on-the-fly adjustments. This is why you tune with wideband.

Wade

iTrader: (1)

Tim,

If you try to do any tuning whatsoever based on a stock type O2 sensor, you are making a big mistake. You would be better off tuning by the exhaust sound, seriously.

Wade

Tim Benton

iTrader: (1)

Correct,

I guess tuning would be the wrong word, although I do use it to somewhat get an idea of how rich or lean I am at WOT. Pulling gobs of fuel out with it is something I know better than doing, thanks to the good ol days with the PFS PMC. To clarify what I sort of meant since I know it goes to the fuel maps at WOT. When the voltages reads .01 to .03 in the decel test I talked about above, I'd then hammer it in 4th gear and the voltage would only get up to .95, which is fine for me until I get a chance to get a wideband on it. When I started noticing the strange decel voltage of .15 to .17 or so, hammering it then would give 1.10 voltage or a tad higher. So if you didn't know the voltages had been scewed upward, and thought, damn I'm running rich since I think .95 is safe, I'll start taking some fuel out of the maps to bring it down. Well, if you mistakenly take out enough to drop it from the 1.1 range to the .95 range, you might be running dangerously lean. My post was kinda of like me saying "hey guys, I just noticed this on my PFC, so be careful if you are taking fuel out based on the O2 voltage, it might not be reading correctly and you might be running lean based on that info".
Thanks for the feedback though.
Tim Benton