1991-1993 240sx: rapid drop in idle during deceleration

[grachman]

The AIV keeps the rich/lean condition optimal during deceleraton and idle.
The O2 sensor completely drops out during idle and deceleration.
Without the AIV valve, the car suddenly becomes very rich below approx 1500 rpm. Would a sudden very rich condition cause a drop in idle? The maf i think would weigh in pretty fast to get things back in balance though. Im just wondering because a lot of people have removed their AIV valve.

I wonder if California people have as much stalling/fast dropping idle during deceleration? Because their o2 sensor stays in play during deceleration as they have different ecu.

[tt99ol]

yes a really rich condition will cause the engine to bog down.

[slider2828]

If you have a problem with taking out the AIV Valve, then keep it in... Nissan designed to be there...

[Dream240]

What's the AIV valve.....? You mean the IACV valve?

A sudden increase in fuel will cause the engine to bog down slightly. Otherwise known as flooding. And it's not the MAF that regulates the drop in idle, it's the IAA unit. Removing the whole unit will cause your car to idle like shit....if at all. IIRC some guys remove the EGR and PAIR systems, but not the IAA unit.

I'm sure there's some guys out there that take it out but I can't imagine why or how to do it correctly.

What exactly are you trying to accomplish?

[grachman]

I got this really wrong. The the AIV(air injection valve) or PAIR valve supplies air to cat to burn up extra fuel at idle. The idle on all non-calfornia 240sx's is rich as hell with or without the AIV. The aiv does not effect richness before the cat. Passed smog test today with my new aiv. My idle remained rich so reading richness at o2 sensor for non-california cars is pretty silly.