I've been wondering why the PCM randomly goes between cells 15 & 22 at wot. Yes, it seems EVAP is messing around. EVAPDC ( purge solenoid duty ) is spiking and PCM drops to cell 15 at those points.

Can I get rid of this happenin somehow ? Car is a '98 f-body.

 

I would like to know this as well.

John

 

It may say Cell 15 or it may say Cell 22 but the
only thing that matters is, whether you have a
positive LTFT in those cells. If not, then the
closed loop correction is totally out of the picture
and the fuel air multiplier you get will be from the
PE or OLFA table (presuming other stuff like COT
is not getting into it).

Now, Cell 22 being a sort of emissions-active
catch-all, will probably be harder to get happy
than the rest but if the rest are indeed well tuned
then 22 should follow. But if you have some of the
regular cells with problems then 22 is likely seeing
the same MAP*RPM points and no happier than
the rest.

 

OK thanks. I have positive ltft in cell 15 and 0 in 22.... I guess I'll just to go back to ltft tuning. COT is disabled. Other than the WOT cell toggling everything seems to work fine, LTFTs are around 0 through VE and IFR adjustments and cells fall in their places as I've set them.

Though, at WOT EVAP should be inactive and PCM should not go to cell 15.. just makes me wonder if the PCM is still fully OK or does the program start to rot. I have SVO #30 and I would remember someone had this same issue starting after upgrading the injectors on '98 f-body.. would seem to be completely uncorrelated but you never know what bugs may get activated through table modifications

 

FWIW I am also running SVO 30# injectors.

 

I'm having the same problem with cell 15 randomly showing up in a single gear WOT pull from 2000 to redline. I haven't had the chance to log anything with the Evap. My LTFT's were positive (6% & 13%), but my AFR was in the mid 12's and COT is disabled.