I have a 2004 5.3 silverado, and from what ive been told changing the switchpoints should have some effect since this is a gen3 5.3, but I cant seem to get mine to play nicely.

I have the switchpoints set to 300 but the average switching voltage is around 550mv which coincides with my wideband showing slightly rich.

Am I missing something obvious or what?

thanks

I uploaded the log and tune and the config file. I renamed the extension on the scanner config file to .doc because we cant upload .cfg here, just change it back and it will be fine.

 

For starters is their ethanol blended fuels in your area where you live and if so is the stoichiometric value in your tune set correctly to match the fuel you are running?


Are you having the issue where you are tuning everything in open loop to 14.68 and then when you go back to closed loop and the narrowbands are trimming back to something different like 14.3 or so?

 

There is a 10% ethanol blend, but does the computer even look at that or just the switchpoints to determine where to change? Problem is I can get it fine in OL but when I go back to CL its rich. I would also like to lean it out slightly for mileage purposes.

 

Right the narrowbands are doing their job which is to switch around a Lambda of 1.00 wich is stoich for whatever fuel you are running whether it's pure gas, e10, e85 doesnt matter, the O2s don't know or care what fuel it is. The oxygen sensors are just going to read the oxygen content in whatever the fuel is and switch around that.

I've seen it many times on many different cars and trucks in my area with our ethanol blended fuels as well in that you can tune in open loop all part throttle areas to a Lambda 1.00= 14.68 and sure enough you go back to closed loop and they will be correcting back richer anywhere between 14.1-14.4 depending on the percentage of ethanol in the fuel and stoich for e10 is 14.13 so if their is exactly 10% ethanol you can bet that those narrowbands are going to be trimming back close to that.

The correct way to fix this is to set stoichiometric in the tune to a lower number for the ethanol and the trims will come in line when you go back to closed loop.

I have seen lowering the switchpoints take some effect in leaning out the fueling in some applications and in others it made no difference at all. The only real way to combat this is to run an open loop tune set to the leaner cruise AFRs that you are shooting for.

 

My confusion came from I thought the o2s just looked at the switchpoint voltage and that was all, but appearently whatever I have set to stoich matters as well as the switchpoints? Im going to try it either way, just to see what happens.