Auxiliary Air Regulator --- Testing and Adjustment

[Wade Nelson]

Auxiliary Air Regulator --- Testing and Adjustment

by Wade Nelson

My 280ZX doesn't start as consistently and quickly as a fuel injected vehicle should, which is immediately on the first crank. Sometimes it takes several cranks, sometimes it'll barely catch and I have to pump the throttle to get it up to a normal idle speed, all of which indicate something isn't right. But from then on it runs great, so I've never worried too much about it. Bigger fish to fry...

I also noticed I don't seem to get much if any idle-up on cold starts, higher RPMs which should gradually decrease.

Themotyme / Cold start injector APPEAR to be working, at least intermittently, so this pointed me towards the AAR. (Yes, I could do MORE to confirm they're working 100%...)

First, I got in the archives here, and then in the FSM. Posts in the archives indicate the AAR unit rarely fails. If it had, Rock Auto has 'em....

https://www.rockauto.com/catalog/x,carcode,1209316,parttype,6072,a,Search%2Bfor%2B1983%2Bnissan

The AAR consists of a rotary shutter which gets rotated as a bimetalic strip heats up and bows, powered by the battery. (of course ambient temperature will also affect the strip...)

The shutter, normally open, rotates shut as the strip heats up.

There is a calibration screw on the unit, typically its painted over to prevent tampering.

What I did was remove the unit from the car. On a 70 degree day, the shutter was completely closed. I used a small pick (icepick) to carefully try moving the shutter. It seems like it was initially slightly stuck, I observed a fair amount of carbon buildup in there. I was careful not to damage it, but after being opened once it then operated smoothly. Maybe I was getting no auxiliary air at all.

Next was cleaning. I'd have preferred to use some stronger CARBURETOR cleaner, but all I had was brake cleaner. Sprayed some in from both ends, sloshed it around a bit, poured it out. Couldn't see that I'd done much carbon removal, but the shutter moved smoothly.

Next I tested the heater with my ohmmeter. 60 ohms, right on the money. Manual sez 25-90, but the unit itself is stamped 60 ohms.

Next I threw it in the freezer for 30 minutes to see if the shutter would open completely. It did not. Only closed about half-way So I decided to try and "calibrate" the thing. This may not be the RIGHT way to do it, but time will tell if it works well enough. I figure at 32 degrees or below I need as much idle-up as it can give.

After freezing, I loosened the adjustment nut, held the shutter completely open with a pick, and re-tightened the nut. (The alternative calibration procedure might be to warm the thing completely up, electrically, and re-tighten with the shutter completely closed)

It would still stay about half-way open after this procedure.

Still cold, I applied 12V to the terminals, and watched, as over the next 2 minutes the shutter SLOWLY closed from the half-way open position. Ok, so at least it should completely CLOSE, which is the most important thing, since I only drive this thing in the summer anyhow.

(Since it's just a heating coil polarity shouldn't matter when you juice it...)

Results? Hard to tell. After letting it sit for 15 minutes while I wrote this, I went out and started it up. It started right up, idled at about 750. After a full 2 minutes it seemed to decrease down to about 650. Of course it's 70 degrees out, so it's hard to expect MUCH in terms of idle-up or down. I suspect on a colder morning the effect, if I helped matters any, will be more apparent.

If not, I may try the alternate calibration procedure of locking the shutter down when it's completely warmed up.

HTH

[Zed Head]

I often think about replacing the automatic AAR with a manual valve, that would work like the hand throttle levers on the very early 240Zs. Manual fast idle control. The problem with the AAR is that it has its own heater so it is not very well tied in to actual engine temperature. Between the time that the AAR heater closes it and the engine coolant flowing through the heater plate under it heats it, there is a period where you can have a low idle.

[Wade Nelson]

Here's an AAR cut apart, showing the guts, on another Z website. FWIW, this site has dozens of great tech tip articles.

http://atlanticz.ca/zclub/techtips/aar/index.html

[Wade Nelson]

Hey Zed --- any reason not to just put a resistor inline with the AAR and slow down the rate that it heats up?

My AAR is 60 ohms, so if you added another 60 ohms, it would take (at least) twice as long to heat up and pull off.

You'd need a 1.2 watt (capable) resistor. Maybe use an old ballast resistor if radio shack doesn't have what you need. Remember, you could take TWO 1-watt, 100 ohm resistors in parallel for 50 ohms @ 2 watts, 3 half-watt, 180 ohm resistors in parallel for 60 ohms @ 1.5 watts, etc...

[Zed Head]

That's a good idea, I might try that. Probably better than just disconnecting the power and waiting for the coolant to get warm.

For such a primitive device, it's surprising how long they kept using them. My 1995 Pathfinder has one.

[TomoHawk]

I often think about replacing the automatic AAR with a manual valve, that would work like the hand throttle levers on the very early 240Zs. Manual fast idle control. The problem with the AAR is that it has its own heater so it is not very well tied in to actual engine temperature. Between the time that the AAR heater closes it and the engine coolant flowing through the heater plate under it heats it, there is a period where you can have a low idle.

I've noticed that too. Even on the hottest summer days, with a warm engine, it goes straight to the higher idle when you start the engine.

I've had the idea to insert a plug into the hose with a small hole in it to allow a smaller amount of air in, so the idle isn't so high, or possibly some kind of manual or electric valve, in addition to the AAV that you can open on cold days.

[Wade Nelson]

Here's another website with some good chat about the AAR

http://www.hiperformancestore.com/Ljetronic.htm

[TomoHawk]

If the AAV gets power when the fuel pump is energized, maybe you could fool it and get it to turn on even before you start the engine? On a warm day, you don't really need that much of a warm up, so it would probably be good to have it close sooner.

Or you could just swap in an electric valve that you control yourself.

[rcb280z]

Another way to test the AAR (especially when cold) is put a vacuum gauge on the intake and start the engine. Vacuum gauge should show lower vacuum. Mine is at 10 in. and gradually increases to 18.5 when warm. Neat to observe.

[Wade Nelson]

Just a caution to noobs, RCB is recommending measuring INTAKE vacuum not MANIFOLD vacuum. Be sure you connect to the right port.

[z e r o]

To the OP, do you get the 5 second fuel prime before you crank the engine?

[Wade Nelson]

It's supposed to prime for 5 seconds after going just to the IGNITION and not the CRANK position? As in squirt the cold start injector, or just run the fuel pump and pressurize the rail?