AFR's at idle

classicauto · 05-20-2009, 08:49 AM

Yes its really a matter of what the engine likes. Mine is most stable around 12.7

Should be able to go a little closer to 13, or even low 13's though.

RETed · 05-20-2009, 11:14 AM

This is why I don't like widebands...

If you read the FSM, it tells you to adjust everything possible until idle is highest.
The FSM does not mention anything about AFR's or widebands - you don't need it accord to what Mazda recommends.

A lot of things can affect wideband AFR's, and it's not going to be identical for all engines.
Most have reported that anywhere between 12.9 to 12.5 is about normal.
The engine just doesn't like idling any leaner than that - probably due to the fact that atomization is very poor at that low RPM's.

Bottom line...adjust AFR's until idle is highest; don't adjust idle trying to hit some target number.

-Ted

vex · 05-20-2009, 11:18 AM

Quote:

Originally Posted by RETed

This is why I don't like widebands...

If you read the FSM, it tells you to adjust everything possible until idle is highest.
The FSM does not mention anything about AFR's or widebands - you don't need it accord to what Mazda recommends.

A lot of things can affect wideband AFR's, and it's not going to be identical for all engines.
Most have reported that anywhere between 12.9 to 12.5 is about normal.
The engine just doesn't like idling any leaner than that - probably due to the fact that atomization is very poor at that low RPM's.

Bottom line...adjust AFR's until idle is highest; don't adjust idle trying to hit some target number.

-Ted

I was/am curious on what peoples idle AFR's are not to adjust my idle, but to figure out if I should consider the smoke I am seeing intermittently at idle could be caused by the AFR's I'm seeing.