Idle work, no VE changes but now runs rich

[maudyZ28]

Hi Guys,

I'm working on a tune for a friend who has had quite a lot of tunes in past. Its running COS3 and have around a 230/230 cam with 241 ported heads and LS6 intake. Basically I'm trying to sort idle fueling doing an auto VE but there have been so many changes to his tune I am finding it hard to figure out where to start.

Tune 1 -> has low ish desired airflow, but upto for in the airflow adders table (usually zeroed ? as this is new COS3 table) WB is a dual FAST but is VERY jumpy (+/- 2) in AFR ie 11-17 averages around 15 at idle. The STFT (semi closed loop in COS3) are -15% to -20% so still pulling fuel, even though WB is averaging 15. Like I say it is jumpy and doesnt hold flat, is there an issue?? .
The IAC area has been shifted also so there are *less* zero values and rest steps set to 310 and not 160 as stock tune.
The car hunts but i wanted to sort fuelling then check spark with DTC but I cant understand why if WB is 15:1 that STFT are still negative.


Tune 2 -> To figure out what was happening I tryed to get back to 'stock ish' values. I zeroed the adder idle table (B4338 - engine compensator) and increase the desired airflow to compensate. (set similar to my car with 228/228 cam and 253 heads). Also reset the IAC area to stock and rest steps to 160. The car starts and runs fine but now is PIG rich, WB is 12.5 (still very jumpy) and the NB are 850 mv constant. I HAVE NOT CHANGED THE VE. How would these changes cause the fuelling to be effected so much??

Assuming rest IAC step doesn't make a difference to fuelling or the IAC area, again assuming it is just a reference to deesired airflow telling the IAC how much to open. Then my theory is that the desired airflow is what is used with the VE to calculate fueling. As I have increase only this to compensate the removal of the airflow adders table does anyone know if this why the car has gone so rich with the same VE? I will post tunes if the guy okays it, he has paid a lot of money for them and we've had to edit a lot to make the car run better. Plus the idle is still crap as I've not changed anything as I need to figure out what is going on.

Once I get a handle on what tables do what then I can sort fueling and then spark. Do people just tune the desired airflow table for idle or do you use the extra adders tables? (B4338). Any should the WB hold steady at a given fueling (my innovate MTX serial does) I'm wondering if there is a WB earth issue with the FAST??