Currently around my area the outside temperatures are 98-100 degrees. During the night they fall to around 85-88. In the hot weather the cars a/f on the wide band is 14.2-14.6. this being stoplight idling and 2500 or below driving, 35-45 mph in town kind of driving. At night it will idle at a a/f of 11.8-12.2, and sometimes a little leaner. Driving light throttle 35 mph or so is 12.5-12.8. Any idea as to why? its tpi, ebl. Thanks

 

Probably some IAT sensor fueling tables you need to correct. ECM has ways to change fuel mixtures based on intake air temps. Usually hotter air temps gets richer but in your case its opposite and needs corrected.

 

i see an iat blend filter, iat/cts compensation, and iat/cts comp bias sa. Which table should i be looking at?

 

Lower numbers means richer. So you richen up when the temp drops.

As suggested, looking at the MAT comp tables would be a start.

I would assume this is open loop, correct?

 

im not finding any MAT tables of any kind, under another name possibly? No closed loop

 

IAT/CTS - Blend Filter

The higher the value the more CTS is used versus IAT. The final value is used as the inverse temperature term for the injector PW calculation.

RBob.

 

I may be misunderstanding, but if the vehicle is in closed loop during the time when the A/F dips down, I guess you may need to check your BLM status to see if you're maxed in the 160 area? Closed loop should give you consistant feedback across the board, and not drop out of stoich unless a parameter has been reached/exceeded. You may be fighting multiple issues in multiple tables/constants, or you are still in open loop as stated.

 

Thanks guys Ill look into these tables