I've read the sticky on AIV removal. I just want to disable it. Is unplugging it sufficient. The solenoid will not have power so will not open and close and will not send vacuum signal to aiv valve to open/close. I don't understand the full operation of aiv so don't know:(

sticky on aiv removal:

zer...age=2

The problem with the AIV is that it gets gummed up and sticks. If it's stuck, it doesn't matter if the solenoid is working or not.

In other words, no this will not work.

The easiest way is to go to Canadian tire, and pick up some big pruning shears, an "Automotive air breather" (a little air filter dohicky), a bolt with a big head, and a couple of hose clamps.

Cut the hose connecting the AIV to your intake, stick the big bolt in the intake side and clamp it down, and stick the air breather in the AIV side and clamp it down.

Now your AIV still works to heat up the CAT quickly, but doesn't let exhaust flow into the engine.

Ok, that makes sense. the reed valve is not closing right so the exhaust is going where it shouldn't regardless of what solenoid does. thanks. can tire does sell caps for hoses. 3/4 in i diameter is their largest.
Modified by vancouverbc at 12:22 AM 7/2/2005

I didn't get a hose cap because I wasn't sure what the inside diameter of the hose my mechanic used when he plumbed my AIV to a high-vacuum location of my cold-air intake (D'OH!).

I disconnected the 1 inch diameter rubber hose where it attaches to air intake. It is the hose that goes from black plastic resonator to air intake.largest cap at can tire is only for 3/4 in outside diameter and cost 6 bucks.i plugged the nipple coming out of air intake with electrical tape. 3/4 inch cap would work but 6 bucks too expensive. i plugged in the white plastic air filter ($2.99)into the rubber hose coming from resonator. so , no cutting of hose involved.

i notice that my idle is now at 900 . normally it is 700. not sure if i read it wrong in past or what is going on.

vancouverbc wrote:i plugged the nipple coming out of air intake with electrical tape.

I wouldn't trust electrical tape for that. if it comes off, it becomes a lower resistance path for unfiltered air to get to your engine, possibly including bits of the tape itself.

that's right. the nipple is past the air filter. i might have to bite the bullet and buy the cap. they had black air breathers for 4.99 which would blend in better . i don't think aircare will like secondary air being vented into atmosphere, albeit through filter. you have been alot of help:)

I opened up where my air filter is and discovered that the metal inlet for the maf is rusted away by water coming in from aiv valve. it is only rusted near where aiv comes in and i have seen water in the hose coming in from the aiv. it totally rusted away my year old air filter.

Modified by vancouverbc at 6:50 PM 7/4/2005
Modified by vancouverbc at 6:51 PM 7/4/2005

my rpm's went up to 1500 after i disconnected aiv from air intake so i took off the entire aiv today but rpm still at 1500. just took off 3 10mm bolts fastening assembly to side of engine bay. i could than rotate assembly and easily unplug 2 vacuum tubes and and 1 inch outside diameter rubber hose going to exhaust. the one inch hose going to air intake/filter was already disconnected. used plugs from canadian tire to plug up the openings.
Modified by vancouverbc at 10:23 PM 5/24/2006

took the aiv vacuum valve apart for heck of it. everything is coated with gunk. the vacuum valve(brass cylinder thing at top) was filled with rust(literally). i guess alot of water from exhaust got in. you just need to undo 2 screws to take brace off and you can take the vacuum valve out while everything else in the assembly is still intact and attached to engine bay.the vacuum valve controls what gets to your air intake. four steel reed valves in plastic casing are controlled by vacuums created by pulsations in exhaust. the solenoid valve is tiny and is right where the electrical connection is.

The pictures shows the brace i was talking about and the reed and vacuum valves. the rust is inside the vacuum valve and not visible.

The brace was covering big hole in top of vacuum valve so i don't know why i did not have trouble from loss of vacuum etc.
Modified by vancouverbc at 9:48 AM 7/5/2005

vancouverbc wrote:my rpm's went up to 1500 after i disconnected aiv from air intake so i took off the entire aiv today but rpm still at 1500. just took off 3 10mm bolts fastening assembly to side of engine bay. i could than rotate assembly and easily unplug 2 vacuum tubes and and 1 inch outside diameter rubber hose going to exhaust. the one inch hose going to air intake/filter was already disconnected. used plugs from canadian tire to plug up the openings.

My idle didn't change at all when I disconnected my AIV from the intake. If yours was really gummed up, someone may have adjusted the idle control to compensate for all that exhaust getting into your intake.

The idle control screw is on the ECU box, facing the front of the vehicle. Mine's turned a few degrees past the lowest setting and my car idles smoothly at ~700RPM.

To access the ECU (1989 240SX), remove the passenger side door sill (do not press on the screws while unscrewing), then remove the kick panel. You'll have to hold onto the flange around the screw with pliers while unscrewing. Do not press on the screws or they won't come out.

Once the kickpanel is off, you should see the ECU and the rear washer fluid line. The ECU bolts are at the top and bottom of the ECU. The top one is hard to get at, behind the glovebox. you'll need a long socket extension (10cm) and a 10mm socket. Undo both bolts. You may need to cut a cabletie holding the lower cable harness.

Now turn the ECU around carefully.

You should now be able to see the idle control screw.

While you have the kickpanel off, you might as well check for codes. do this by turning the ignition on (don't start it) then turn the idle screw all the way to the diagnostic mode mark. Wait untill the lights flash 3 times in a row, then turn it back. Watch the lights. The red one will flash first, then the green. when you've read off all the codes (and written them down) Turn the idle screw back to the diagnostic mode and wait until it flashes once, then turn it back.

If you got anything but a code 55, your car probably needs to go to a mechanic (or you could look up the code yourself and fix whatever is wrong).

To set the idle, start the engine, and slowly adjust the idle screw until it's idleing at what you want.

My check engine light is not on except when i first turn ignition on so I assume I have no codes? and self-diagnosis would be waste of time?

That makes sense re the previous owner adjusting idle up to compensate for faulty aiv. I found this procedure to for adjusting idle in old FAQ for "1991 240sx:

Adjusting the idle is pretty straight forward:

Disconnect the TPS harness and turn the idle adj. screw on the IAA to get the car to idle at 650 rpm. Reconnect the TPS harness and your beloved should purr at 700 or so rpm. (The Factory manual gives a +/- tolerance of 50 rpm.) The IAA is at the back of the intake manifold. You can see it standing over the right (passenger side for N.A.) fender and looking at the funky device with the dime size recess for the adj. screw."

Checked my ecu today and found two codes(11,21) which went away when i cleared unit and test drove . Obviously, not all codes turn the check engine light on.

My idle screw on iaa unit is all the way in and my idle is still at 1300. I noticed that my idle goes up when i clean the throttle. I cleaned throttle at same time as i removed aiv valve so i think cleaning throttle valve ups my idle. I have to conclude that previous owner must have adjusted throttle linkage so i have to too to get back down to 700 rpm. my rpm used to be 700 rpm.

pinch off the one inch hose coming off the intake tube that runs to the idle control valves. If the car still idles and you have the IACV[iaa] screw all the way in, you have a vaccum leak

Thanks:) I unscrewed small adjustment screw on throttle linkage and got idle down to 650 rpm. when i first depress gas now it feels sticky. anyway, i never had high idle until i removed aiv, cleaned throttle, and cleaned grounds.

Your not suppose to touch that screw. It is a calibration screw set when the throttle chamber is manufactured. It is not there as an ajustment. It sets the throttle plate so it will rest with out binding[sticking] in the chamber.

Thanks:) I will make sure it is set high enough so it does not stick. I think previous owner adjusted this to get higher idle to compensate for bad aiv etc and dirty throttle etc so hopefully i will be putting it back to where mfg wanted it.

Spray it glossy black--it looks better
Modified by mick at 6:21 PM 9/3/2009