Air don't pass both ways on the AAR when closed genius. In fact the internal design forces the sealing from one direction genius. :)

Jdub is correct - it is the 12v current that fully close it when starting warm. That's why you get a short period fast idle when starting up when the motor is warm.

ok. maybe that was a bit harsh, sorry. one would think that the air would force it shut. i have one on my kitchen table and am testing it, and have tested it multiple times. sometimes the passage IS air tight and sometimes it isnt. i just got off the phone w/bosch and they say the vacuum is supposed to seal it shut and maybe i have a vacuum problem. just went to the car and tested the vacuum and supply to the AAR, both are funtioning properly.
what bugs me is this: the first one lasted a month, the second one a week.

Jason, Have you checked the condition of the "Y" shaped rubber hose which feeds both the AAR and AAV? Also the condition of the rubber nipple on the ribbed boot (the one on the top of the air box) that it the "Y" shapped hose attaches to via a metal elbow. An air leak here may cause may cause some strange idle problems as in all the air that is going through the AAR (when cold and open) coming in from the outside and not passing the air flow metering plate. If the idle air bypass or mixture is set to keep the car idling correctly when cold with this air (vacuum) leak then when the AAR heats up and closes the car would idle faster. Good luck, Jim

havent actually checked the condition of that hose. kinda hard to even see with the engine in car. i did verify that the supply to the AAR is clear and unrestricted, i did this by attaching a length of 3/8 hose to the valve when open and blowing through it. pulled the vaccuum side off and verified suction at that end. everything checks out. i think that the "y"hose is good because when i plug the AAR all is well, no leaks and no high idle. i think for now ill have to just do without a choke until i can figure this one out.

I don't think blowing through the supply side of the hose to the AAR will find an air leak to the outside; blowing likely will not find a crack or split in the hose. I know how cramped this AAR, AAV and EGR area is; I found it difficult to work in this area with the engine out of the car! Last year when I had my engine out I found my "Y" hose in pretty bad shape (26 years old and already repaired in a couple of places with shrink tubing); I replaced it despite it's expense while it was relatively easy to get at. Good luck, Jim

so you gave up? I can't give up my car won't run... I was thinking this might be my problem too but mine is starting great and stalling great... I have to get in there and check vacume leaks... I just want to kill someone but I don't know who!

after all that it ended up being a dirty power connection to the AAV.
the engine heat alone is not enough to keep it closed, it needs the internal heater

First, let's try and understand the problem
and the components' functions.

1. The WUR (warmup regulator) affects
the fuel mixture for cold starting by changing
the head pressure on the CIS fuel distributor.
It should only make the engine run too rich
or lean when cold. It basically should have
no effect when the engine is warm. It will
not cause the idle to be at 1700.

2. The AAV (aux. air valve) affects the idle
when cold. The device should have electrical
connections run from the fuel pump circuit.
The valve should be fully closed when the
engine is warm. The valve closes with engine
run time. Don't try and adjust the idle when
the valve is not closed, because the cold
start idle will be too low.

So, check the power coming to the AAV.
You should have 12 volts with the engine
running.

Also, make sure that you have no intake air
leaks which bypass the throttle body.

Good luck
Lorenfb@aol.com

Just my .02 worth, I was having cold-start problems, backfiring, idle bouncing all over between 1000 and 2000 rpm, finally I took it in to the mechanic and he found that the WUR was bad. He replaced the WUR and cleaned up some wiring (I had already replaced the cold start valve, fuel filter and accumulator and thermo-time switch) and the car is as good as new. I didn't have the pressure gauges to test the WUR, but now I do.

Many of you have followed my intermittent "cold starting" problem that eventually became a constant starting problem that caused my to have to crank my car 20-30 times, with several loud backfires, prior to the car starting. Once the car started, it ran great but the starting problem was driving me nuts. Needless to say, I replaced alot of components (fuel filter and accumulator, cold start valve and thermotime switch, throttle microswitch, plugs, CD unit, rotor, coil, Pertronix unit, WUR, etc...


Each replaced item improved the situation temporarily, but the problem still persisted. The cold and warm pressures were within acceptable limits and I had good spark at plug #1, but the car just cranked and refused to start. To make a long story short, this is what the mechanic found:

- The plugs were improperly gapped (too wide) even though I followed the instructions on the PermaTune CD unit for spark plug gapping specs.

- The plug wires and their "boots" are bad and I will replace them

- The "new" throttle microswitch that Jordi Riera sent to me worked perfectly and the old one was bad

- One of the wires coming off the Pertronix unit had rubbed until the insulation was off and bare wire was showing.

My mechanic "fixed" these things and the car starts on the first crank, idles at 950rpm and runs great. I REALLY appreciate all of the assistance so many of you have provided. I have learned alot from you kind folks. I'll post this update on the other posts that I have been on so that anyone with a similar problem may be helped. I had checked the spark at plug #1 and had a nice spark, but my mechanic showed me that others were weak. I hope this helps others out there....