strange O2 trim behaviour at idle

[Bohrn]

So, I was playing around lately with the datalogger cause the car wasn't feeling quite right.

Got the WOT tuned, nicely again, as I had frigged it up earlier.

But idle is wierd. Heres the thing. I had my safc set at -18 for idle.

O2 trim was at about 105% and the low trim was falling steadily. Crappish mileage lately especially at low speeds and idling. So I figure I'll take out a few percentages at idle and clean things up. But, after 2 or 3 seconds of being nice and lean, it takes a nosedive right back to around 100%.

take out another 5%, same thing.

I am now at -45% and it STILL is trimming out at about 105% low trims are a bit better at around 125 but it won't hold it where I put it. Its ok at the other rpms, both free revving and driving.

Sensor cycles, but not smoothly. Pressure is steady. Idles nice, and when I had it on the 4gas at work the other day it was very clean.

any help, thoughts and or ideas(on the helpful side) would be appreciated.

thanks

 

[flytalon93]

Trying to understand your dilema. Are you trying to get your low fuel trim at 125%?

 

[Bohrn]

yea, I normally run my car at around 125-135. Over the years I have seen alot better mileage, throttle response and AirCare testing with these sorts of trims.

Not really the point tho, no matter WHAT I do with the SAFC, I CAN'T make it go higher than about 105%. I can take out the full 50%, or even add that much. Car will run like crap obviously, but the O2 sensor trim(yellow one on TMO logger) will only stay lean or rich for a second or 2 and then move back to around 100%. When its on the 4 gas analyser at work, the mixture IS changing, its just not registering with the logger.

I and a couple of others believe that the sensor is just slowly dying. I am going to replace it.

Speaking of that, anyone heard of those newer Denso ones? Supposed to be higher resolution and faster response. Can't remember if they are Irridium or some other super duper sounding name.