I have a 94z28 with a lt-1 scanmaster and a Maft Translator. 1st run showed a02 reading in the 250 range and 5.8 kr with the maft run straight up(stock).Run 2 02 reading was 882 and5.7 kr w/maft set 2 percent lean. Run 3 02 reading again was 250 and7.3 kr w/maft set again at 2 percent lean. Run 4 02 reading was 871 and 10.5 kr w/same maft setting as before.Car ran a best of 8.90@80 and was in the 8.9 all runs with 79.4 the lowest mph.Why are the o2 readings so low on some runs? Btw i replaced the 02 sensors in summer of04 and was using HUSKY/ MOHAWK(92 OCTANE) which is ethanol enhanced. The temp was between 75/80 that day. I have used Husky(94) before and had no kr and proper o2 readings .Iput in CENEX(91) the next day and my o2 reading was920 w/0.5 kr so i dont know what is going on!

 

Have you checked for vacuum leaks?

 

How much ethanol is in the fuel? Ethanol brings its own O2 to the party, and the stoichiometry of ethanol is different than gasoline. It may also be cooling off the combustion process, and when the exhaust gas temp changes, it causes large changes in the O2 sensors "rich" side readings. That's why you can't rely on WOT O2 sensor readings, because they simply aren't accurate at the rich A/F ratio required for max power/torque.

At what MPH/RPM are you getting the high knock retard values on the ScanMaster? It isn't unusual for the ScanMaster to show high peak values of knock retard at the shift points. Recalling the MPH from storage will help you determine if its happening at the shifts.

I won't even comment on using the MAFT to "tune"

 

I think the question you need to be asking is why are you getting knock retard like that. It would also help if you have a signature with a description of your car and it's mods.