Idle Air Control System Adjustment?

[onespiritbrain]

i know i saw someone else asking this same question not too long ago but i could not find the thread. 

 

since installing an electric fan i believe i actually have more mechanical resistance when the AC is on and the electric fan is on high because the RPMs dip down a little lower than before the electric fan was installed. its probably 50-75 RPM down from 750, so 675ish at times. my wifes car kicks it up to 1000 RPM when the AC is on and id like to end up in that area.

 

now what i want to do somehow is cause the IACV system to add a little more air when the AC is on. ive gone thru the FSM and it looks like its no dice for making adjustments per any instruction. however i did see some instructions about removing the plunger from inside the FICD valve..

 

the AAC is a time proportional valve controlled by pulses from the ECU and we dont have any hope of making adjustments to the ECU that i know of. the FICD is just on/off so my thought is to decrease the diameter of the plunger so that when the valve is on more air is allowed to flow. of course i will have to grab a test part from the junk yard.

 

my worry is that with increased air flow and the resulting increased RPM, the ECU will just immediately turn the FICD off when it sees higher than desired RPMs and the result will be surging as the valve turns on and off, on and off..

 

is there another way to obtain the desired result of higher load RPMs??

[Mr_Reverse]

The IAC should kick up the idle a bit when the A/C compressor is switched on, but for the rest, the ECU will try to keep the engine at it's programmed idle speed. I can't recall if the idle speed can be changed through the ECU on the VQ35 that has the throttle cable, but you can adjust the idle speed screw if you want a higher idle. I know you can adjust the base idle speed with Consult or a good scan tool on the ones with the drive by wire throttle. Have bumped the idle speed for a few of them per customer request because they felt the low idle was too rough. 

[onespiritbrain]

i should have said this is on a VG33. the base idle speed is dead on 750 with no AC. before the electric fan install when the AC was on the IAC system put it on 800 or so but now its dropping into the 600's. this morning with my AC on i turned my defrost on to burn off the dew on my side mirrors and the RPMs dropped even lower but the IAC adjusted itself back up to the high 600's. Its like the ECU cant adjust for the extra strain that has been added or simply doesnt know that its off by 50-75 RPM.

[onespiritbrain]

A little while ago I shifted into reverse just as I was reaching full lock and the RPMs dropped below 400. If the defrost had been on it may have come close to stalling.

I think I will attempt modifying the FICD plunger. When I do, I will update this thread.