Today i went to adjust the idle mixture screw, turning it about 1.5 turns IN. Now, maybe it is unrelated, but i was logging with my wideband and my AFRs seem to be about 0.5-1.0 RICHER. does this make sense?
if it is true, i am assuming the idle mixture screw is allowing LESS air in, even though the same amount is metered by the AFM?
this is on a stock ECU with SAFC-II doing fuel adjustments. i had it tuned pretty decent before around 13.0-13.5 AFR at WOT across the range, and now i am back down to 12.0-12.5.

 

anyone?
it was also a little cooler than usual, but i don't know why the stock ECU would adjust that much more rich because of different intake temps.

 

the variable resistor has nothing to do with how much air is entering the engine.. the adjustment overrides the AFM signal slightly and allows for some adjustability at idle for the mixture, what it does is tells the injectors to add or remove fuel and has nothing really to do with the air entering the engine.

 

S5 don't have Variable Resistors.

 

i am talking about the idle mixture screw on the TOP OF THE THROTTLE BODY.

 

Hmmm, i adjusted this recently and it felt like i did lose a little power, would this be why? i adjusted it probably no more than a half of a turn. it wasnt a drastic reduction, but i was kind of confused when it happened. I have a bone stock 88 n/a, other than straight pipes to OEM mufflers.

 

sorry, maybe i was using the wrong term for this. the FSM calls it the "air adjust screw":

 

i see, i doubt AFR change was caused by adjusting the idle adjust screw, that is just bypassing already metered air.

 

hmm, well that was really the only thing i changed.
i will maybe go out and datalog, and see if it is still rich, and then try adjusting the screw and see if it makes a difference or not.