OK. For the last few days I've been trying to figure out my lean start-up problem and it came down to a faulty front 02 sensor.

Now Im not sure if this is going to work for everyone but I got it to work. First off you will need a wideband 02 to see where the car sits at idle and cruise. Secondly you want to disconnect the front 02 sensor from the main harness which is on top of the valve cover. Then go down the road slowly and watch where the afrs are hovering and adjust your 0% load colum accordingly.

Once you get a target of 14.3-14.7 (trying to stay a bit rich) look at your fueling in the 0% column and your 10% column, they should be pretty darn close first off or you will get the dreaded crossover hesitation. I try to stay within 1-1.5% from the 0-10% column.


Has anyone else tried this?

 

I only adjusted the 4 points around the idle rpm and used afr at initial start change-over on the tuner after countdown. Once the ecu takes control the afr it seeks and holds 14.7. I left the rest of 0% fuel untouched, in fact, I haven't modified fuel trim until 30%. Instead I modified the injector sizes to get smooth transition. I did have my ecu reflashed for the 660's though.

 

I pretty frequently tune my open loop low load cells by disabling my front O2 sensor.. I got a bit of flak for suggesting it, but I have an actual switch wired into my ECU harness that lets me turn off the signal to the front O2 sensor to force the car into open loop.. Its easier for me than studying the fuel trims to get the best tune for cruising.. And your right, it lets you get your OLF transition dead on..

 

hrm, interesting. I haven't tweaked my stuff in a while, and i probably need to.

 

that is interesting !!

 

dont forget that in closed loop the ecu adjusts the Short term fuel trim settings based on narrow band O2 feedback, the ecu seeking to adjust target afr at idle is very common with most piggy back/ecu solutions, I see the same thing happening when I tune with DSM link, but fortunately you can modify the STFT settings in their software to compensate.