Auxiliary Air Regulatory Adjustment

1982911SCTarga · 06:52 PM

Thanks to Ron's valuable post and pics regarding the CIS auxiliary air regulator, or AAR (the thread is located here: AAR Revisited), I figured out something interesting today that I haven't seen much written about.

My '82 targa has had a low idle issue on a start-up on warmer days when the ambient air temp was in the high 70s or greater or on a warm start on cooler days. What this meant was that the car would idle at around 400 RPMs or so until warming up after five minutes or so. Once it was fully warm the engine would run fine and perfectly idle at 950.

Following CIS basic troubleshooting charts, and with everything else checking out (cold control pressure, system pressure, mixture, lambda system, no vacuum leaks, etc.), the low cold start-up idle pointed to the auxiliary air valve as the problem, in that the engine wasn't getting enough air at start-up to provide for a high idle.

My targa's auxiliary air valve ohm'ed out fine, so the issue wasn't electrical. The rotating disc seemed to freely move so that didn't seem to be the problem either.

Hmmm. What to do? Following Ron's thread, I drilled the rivets on the targa's auxiliary air valve to get a look inside. Everything was clean and seemed to be in order. When I looked carefully down the squarish barrel of the unit, I realized that there is a means to adjust the unit.

The bimetallic strip rides on a pin that is mounted through the side of the unit. The pin is the smaller of the round holes on the end of the AAR. The larger hole is for the plug, which basically covers the nut that holds the bimetallic strip/pin assembly together.

To adjust the hole opening of the rotating disc, you can either move the smaller pin further into the AAR housing or move it out. Moving it in decreases the amount of start-up auxiliary air. Moving it out provides more.

It's a simple thing to move the pin in (again, providing less air) by taking a suitable sized punch and tapping the pin into the housing. Moving it out is more complex because you have to first tap the smaller pin all the way into the housing to dislodge the bigger plug on the opposite side. I did this, tapping the pin in as far as it would go (you'll feel the resistance at the end of the pin's travel) and then removed the plug with a gentle tug from pliers.

Once I did this, I tapped the smaller pin out until it was flush with the AAR housing. I reassembled the AAR, including tapping the large plug back in, and using nuts and bolts to replace the rivets, and tested it in the car. This overshot the mark by a large amount, but my start up idle was around 1,700, so I knew I was conceptually going in the right direction. Since it's easy to tap the small plug in (providing less air), it's better to overshoot on the first go-round.

I did two more adjustment sessions, carefully tapping the small pin in each time, and then testing in the car. On the last session, the car started up at 1,300 RPMs and within a few minutes settled into a solid 950 idle. Sweet. Or as Edd China would say, "Job done!"

If you've got odd, but consistent start-up issues and everything else checks out, this might be something to look into in terms of making a careful adjustment.

Brian

I just realized I made a mistake in the title of this post. Moderators, could you change this thread's title to "Auxiliary Air Regulator Adjustment"? Thanks!

jwakil · jwakil's Garage

Good to know. I have a slightly different symptoms but might solved with same thing. I have very low rpms for the first ~20seconds on cold start ups, which sometimes causes stalls, but always recovers

1982911SCTarga · 07-04-2010, 04:14 AM

Thanks, I should add that to do this adjustment (providing either more or less air at start-up) you do not have to disassemble the auxiliary air regulator. The only reason I took mine apart was to inspect the internals and learn about how the unit could be adjusted and what was possible.

Brian

Paulporsche · 07-04-2010, 05:02 AM

Great work. Another layer of the "mysterious" CIS onion gets peeled away.

enjefriy · enjefriy's Garage

Coincedently, I did do this some 2 months back. Wat I like to add, based on wat happened to me, is that initially, I tapped it to such a location that I could visually see the half moon disappear, with the bimetallic fully heated electrically. (what I shud hav also done was to also confirme that the valve was indeed sealing by sucking on the arrow tip side of the valve, to ensure that no leaks occurred passed the valve once shut.
I add this step, bcos my rpm would not lower to warm idle based on visual setting. The plate needed to overlap the hole a bit more in order to effectively block the hole, as the suction air would seat the rotating plate.

enjefriy · enjefriy's Garage

Also the adjustment here allows for the mechanical repositioning of the valve, which is by changing the size of the exposed hole. Wat I wanted more off was to extend the period where the valve was opened. This I was only able to do by making a cutout switch to the power to the bimetallic strip. Havin located the power feed line to that bimetallic strip, I also located the same supply to the WUR. In This circuit, I installed a relayed switch, which allowed me to delay the heating power to the AAR, & incidently the WUR.
This gave me the higher idle, also richer fuel, as the WUR heat was also delayed.

This works, however it's not automatic as I would need to flick the switch back to allow the heating supply back on.

JFairman · 07-04-2010, 11:40 AM

The WUR and AAV get their 12 volt power from the fuel pump relay so you can splice into the wire there and put in your switch or a spdt switch with a variable resistor like a 8 ohm speaker L pad wire wound potentiometer to experiment with.

On a 930 with 2 fuel pumps the WUR and AAV get their power from the rear fuel pump relay.

T77911S · 07-06-2010, 03:49 AM

nice work. i hate to be one of those that looks for something wrong, and i wasnt, but the AAV is the large disk in the rear that works off of vacuum. it is used only during starting before the engine fires. the AAR is the one on the side, it has the 12v connected to it. again, nice job.

really regulator is a deceiving name for it. anyone that works on electronic FI and understands what the idle control valve or idle control regulator is, may be miss lead by the name of the AAR besause unlike the ICV, once the engine is warm, the AAR has no function, just like the AAV has no function once the engine fires and the vacuum pulls it closed.

1982911SCTarga · 07-07-2010, 05:43 AM

I've alerted the mods to change the incorrect title of this thread (note the references in the initial post text are correct).

Just to report back, I'm getting excellent one-key-turn cold start-ups now with a nice transition to the spec idle speed during these recent 100+ degree days. This is much better than needing several start up attempts and having the engine eventually start at a very low idle and working its way up to where it should be.

Brian

1982911SCTarga · 07:00 AM

This is funny, now, thanks to my poor typing in my message to the moderators, this thread's title now is "Auxiliary Air Regulatory Adjustment." Is the EPA on the case?

Eventually we'll get this correct.

Brian

jwakil · jwakil's Garage

Can someone please post a pic of the adjustment pin which you are supposed to tap to increase/decrease opening? I'm tired of 'the smaller pin on the end' description. There are several pins on the body.