IAC Valve Adjustment '95 Q45

[GseaQ]

This post started as a reply in the Q45 forum. I copied it here because this is where it belongs.

Hi guys,

Our '95 was idling quite high when we got iit a month or so ago - about 850-900 RPM. I checked all the cables with the engine hot and they were all as described in the FSM. I even set them to the "loose" end of the spec range. Then I adjusted the IAC valve until I got the idle down to 600 RPM.

Well, after reading Wes' comment to set the IAC to 2 turns for a base (my interpretation) setting, I thought I'd check where it was now set. Actually, the engine does seem just a tiny bit lean just off idle. That's what got me wondering.

Anyway, the result was the IAC screw was out just one turn. Is this enough? So today with the engine hot and off, I set the screw to 2 turns out. Upon starting the engine, it went from 1200-1500 RPM for a few seconds and then settled at 750-800 RPM - too high for me. I turned the screw in 1/2 turn and got the idle down to 725-750 RPM (indicated) - still too high for me. I want 650 which I'm sure will require nearly another 1/2 turn in.

As a side note, when resealing the valve covers we discovered the vacuum hose to the EGR valve was cracked open pretty bad (like it was cut halfway through). Oddly, the car still ran smooth and strong. Anyway, we replaced the hose.

Any ideas? Another vacuum leak somewhere?

Thanks,Glenn

[Mint Q45A]

I am not sure the number of turns really matter, especially considering that you seem to be bypassing less gas to get the required RPM. If the idle is right I wouldn't worry about it.....but I am not an expert...

[Q451990]

Remember to unplug the AAC valve while you're adjusting it. Also set the climate controller to "econ" and turn off all accessories. This prevents the ECU from trying to compensate for the adjustments you're making.

Heath

[GseaQ]

Thanks Mint,

You may be right. I saw somewhere that when adjusted correctly it would have a 10% duty cycle. I guess I'd need a Consult or some type of scanner to check that. I just know that it has better off idle performance when it's idling at 750 than 600. It loses that little off idle "bog" or flatness.

Glenn

[GseaQ]

Hi Heath,

Does it matter if the engine is running when I pull the IAC plug and plug it back in?

Glenn

[GseaQ]

Heath, disregard. I checked the book!

[maxnix]

I am not sure the number of turns

2.5 - 3 out from closed, presuming the intake plenum, TB, EGR are all clean.