Auxiliary Air Regulator

[JSV798]

Car: 1978SC.
Problem: Car starts normally with high(ish) idle but after a couple of minutes idle speed drops and engine wants to stall. Once engine is warm it idles at a steady 900 rpm. Suspect AAR
What I've done so far:
Disconnected AAR and started from cold and allowed engine to just idle. Engine idle did not drop below 1000 rpm.
Removed AAR and checked resistance - reading was 38 ohms which seemed to agree with what others have found on this forum.
Observed opening in AAR - at room temperature (22 C) didn't look like it was open much - see photo:



Connected 12 volts to terminals and valve closed in about 2 to 2.5 minutes.

Put AAR in freezer overnight and took another photo:


Conclusion: AAR is working but looks to be closed up too much when cold (22 C). The question is: is it possible to adjust the size of the opening? It looks like the bimetal strip has warped. Can it be bent back to its original position? I've seen on this forum someone drilling out the rivets to get at the strip. Is this worth attempting?

[Bill Douglas]

My '79 SC, same stuff more or less. It was doing odd things when cold, high reving etc. I pulled the AAR to bits looking for something odd and found nothing amiss, so I cleaned it although it looked clean, and put it back together. The problems went away and it was fine for the next ten years.

[T77911S]

mixture could be slightly off.
when it closes its like taking your foot off the gas and the RPMs dropping too low.
the cold engine makes it show up.

try removing it again, start it with your foot on the gas, like the AAR is open and then let off, see if it does the same thing.

[JSV798]

Can anyone out there give me a shot of a working AAR so I can compare openings?
And how long should it be before it closes on warm up?

[boyt911sc]

Originally Posted by JSV798

Can anyone out there give me a shot of a working AAR so I can compare openings?
And how long should it be before it closes on warm up?

JSV,

There is nothing wrong with your AAR-201. The opening cross sectional area @ room temperature should be about half and yours slightly smaller. You did not mention the engine speed during the initial start. On the average, 2~3 mins. was the range time I got from my tests with AAR -201 with 33 Ohms (ave. resistance value). Could you check again your resistance (Ohms)? So what problem are you having with your CIS? Thanks.



Tony

[JSV798]

Tony,
Thanks for your input. I was on the point of buying another AAR (seen one for £120 - about $160 but might still buy it as a spare). Measured the resistance twice and it came out at 38 ohms on my meter. Just started car now and on a cold start idles at 1600 rpm for about 40 seconds then idle drops quickly to 1000 rpm and then after about a minute to 600 rpm and then starts to hunt between 600 and 800. Revs will drop to 600 then abruptly move up to 800 sometimes 1000 before dropping back to 600. Once engine is warm idle is rock steady at about 850 rpm. I'm getting good fuel mileage - 27 mpg (Imperial gallons) on a recent trip that included lots of idling in traffic.
Since this is a warm up problem thought it must be AAR or WUR so now suspect WUR but don't have a fuel pressure testing kit. I expect it's time to buy one but not sure how to get one that will fit.

[gazzerr]

Mine tends to close too quickly in warmer weather, i.e. 2 ~3 mins. The engine is still too rich at that point so it gets grumpy. If I set off without just letting the car sit it gets to idle temperate and a steady idle fine.

You definitely have to check those fuel pressures and make sure your idle timing is right, you have good plugs and wires and no vacuum leaks and all that. I have also found that the battery must be properly charged if it's been sitting for a while.

This isn't modern digital fuel injection either, so I have lowered my expectations on it handling the warmup cycle in all temperatures a bit too . It is very reliable as long as all the components are in spec.

[Bill Douglas]

As I mentioned earlier; cleaning it is a good start before you start getting too technical. You may be surprised how well it works when clean.

[john walker's workshop]

Try 1000 rpm warm idle. Did you ever check your CO?, timing?

[JSV798]

I saw a used AAR of the correct part number on eBay for £120 (About £160) and thought it worth buying. Just got round to fitting it and idle from cold start-up now back to normal so definitely worth it. The replacement AAR had a noticeably larger opening than my original so takes longer to close. I'm just left wondering if it is possible to increase the opening on my original unit: maybe open it up and cut a bit more out of the disc; fit a stronger spring; try and bend the bimetal strip a little?