911SC idle question - Page 2

Rich Lambert · Rich Lambert's Garage

Okay, time for some clarity. Here's a couple of pictures of, what I believe to be, the AAV, with the AAR below and in front of it. You can see the open port and the disconnected hose.

Rich

tsuter · 02-25-2003, 02:28 PM

Very interesting. I think someone put the wrong valve in there. They put a Decel valve in where a AAV should be. The clue is the metal line off the AAR does not branch. I don't believe that these two parts are interchangeable. But maybe they are.
In any case if it is a Decel valve installed in the AAV position then it is closed when the motor starts and does not open without a vacuum - and there is none attached. So that is not likley your problem assuming it is always closed. If it is stuck open then it could be.
I would still test the AAR below it first.
Also check that the metal line off the AAR goes around the back to a Y one of which trails back to that valve. The metal line should go to the outside connector on the AAV - not the middle.
As well as leaks in that bolted off vacuum line.
What year is this car?

tsuter · 02-25-2003, 02:35 PM

I saw this is a 1982. I'm beginning to think that someone eliminated the decel valve by back dating the Auxiliary Air System from the 1/7/3 version which you probably had in a 1982 to the 1/7/2 version. In doing so they plugged the vacuum line that used to go from the front of the Decel valve to the throttle body. If you can chase down that line, I would remove it and plug the nipple on the throttle body witha vacuum plug.
They also replaced the metal air hose with the back dated version and then installed the incorrect AAV and it looks like it was installed backwards.
Now the good news is that it may not matter what they did as long as the AAR is functioning OK because the AAV is pretty useless anyway unless it leaks.

Rich Lambert · Rich Lambert's Garage

It's an '82. So...it sure looks like the blocked off hose goes to the open port. If it was the wrong valve, would that be there?

One more thing...the idle is only high when the car is cold. This lasts the whole 9 mile drive to work in the morning. In the afternoon, it idles about 1.6K for a while and then settles down.

Rich

tsuter · 02-25-2003, 02:51 PM

Yes the Decel Valve and the AAV were in the same area so a vacuum line would have normally gone over there. If it goes around the back to your throttle body you''ll know for sure. It looks to me like the decel valve was removed and the line was then plugged. The AAV however appears to me to be the wrong part and installed backwards.

In any case a fast idle when cold (which it is supposed to do for a while) is most likely the AAR not closing all the way. It should fast idle to 2000RPM+- and then slowly come back as things warm up several minutes would not be nonnormal. Heat transfer is bad when the weather is really cold so there is a heating element inside it. There are two wires to it and possibly the heating element is out or not working thus the AAR is staying open longer than normal until the motor heat or ambient temperature helps to close it.
Your last post seems to indicate that and earlier posts were very on target on how to troubleshoot the AAR.

Rich Lambert · Rich Lambert's Garage

tsuter, thanks for taking the time to explain to me how this stuff works. Your description of how the AAR functions and possible problems reminded me of John W.'s post.

I tapped on the AAR with a little ballpeen and the idle settled down to a steady 800rpm. I guess this means something's hanging up inside the AAR. Does this thing come apart? If not, where would I spray carb cleaner to free it up?

Rich

tsuter · 02-25-2003, 03:29 PM

It can get gummy with oil fumes etc blowing through and then it sticks a bit. It has a thin sliding half moon shaped metal strip that blocks a hole. I doubt it is effective to spray anything in the hole. I have one out in the shop. I'll look and see if it can be disassembled. I don't believ so. Generally they get replaced.

MotoSook · 02-25-2003, 03:36 PM

Well you guys beat me to the punch, but here is what I was typing while I was working.

Glad you are making progress Rich. Tsuter, good call.

------------------------------

When I was experiencing a high idle, I pulled my AAV, and to check if it was closing, I suck (talk about shade tree mechanic, man) on the manifold side of it. If it closes and seals while there is vacuum in the manifold it is fine. My 78SC motor has a system that is similar to what some tried to replicate with your AA system. It should close when the motor is running. All of what has been said is true, bit it could be difficult to a CIS newbee to digest.

As tsuter has indicated, if someone tried to replicate the 78-79 AA system, they used the wrong AAV, but if it is closed when the care is idling, it is not hurting you. The Bentley manual has good pictures and explanations on the subsystems of CIS.

So as tsuter suggested, check you AAR. It is not difficult to remove while the motor is in the car. (Note: You CAN use a flashlight and a mirror to see if it is closing when hot.) After 9 miles of driving in 40 or 50 degree temps here in Illinois, my idle would surely settle to normal. So you AAR my be suspect.

If you remove the AAR, spray carb cleaner into it and clean that sucker out. AS JW suggested early on, this will help if you have crude buildup in the slot of the valve. Repeat until you are confortable, and let it dry before you reinstall it just to be safe (I don't know why). It should be quick. Use some medium grain sandpaper to clean the bottom of the AAR and the mounting surface on the motor. I found that corrosion is possible there, and it will reduce the rate of heat transfer. Aluminum does corrode and crude can build up. May not be all oxidize aluminum though.

Check for voltage on the connector that connects to the AAR. When removing, don't lose that little clip thing. I pry it out wit a very small screw driver and use my finger to keep it on the screw driver. A one hand operation.

tsuter · 02-25-2003, 03:42 PM

It is pretty soilid state. No easy way to open. However you can spray solvent in there and then work the bimetallic spring back and forth in the hole with a screw driver or pencil. You could probably do that while its in the car as well by disconnecting the outside metal hose and pulling it back a bit.
It is not too hard to remove except the AC bracket is in the way a bit. The AAR has only two bolts one on each side in the middle.
These things are also adjustable for when they get worn out enough that they don't fully close when warm. Adjusting is a subject for a separate thread.
My guess is yours is stuck a bit and as JW said often its the easiest things that cause the problem.
Good news that whetver the setup is on your AAV that it is not likely the problem.

02-25-2003, 04:46 PM

Rich-
the deceleration valve is what we're seeing in the photo! Its connected right where it should be (apart from the small diameter vacuum line hanging loose). The AAV is out of sight in the photos but it should be there- its further to the front of the engine compartment (ie. AWAY from the camera) & slightly higher than the deceleration valve, kind of behind the airbox. If you reach your hand back there you should be able to feel it (same shape as the deceleration valve).

tsuter · 02-25-2003, 05:53 PM

Whew! Maybe that solves it. Now all we need is to get the parts diagram 1/7/3 updated to reverse the positions of those valves. Wouldn't be the first time. Hey, even Bentley has the air flow direction wrong on the AAR.
1/7/2 is correct for sure.

Rich Lambert · Rich Lambert's Garage

I just came in from the garage. I saw the real AAV valve way back behind the deceleration valve and I'm glad I don't have to mess with that.

I took the hoses off the AAR valve and poked a screwdriver in the side that connects to the metal pipe, but didn't feel anything like a spring (it's on the other side, right?). I couldn't get around to the other side. I did start the car up and, at 35 degrees outside temp, it idled up to about 1.5K and then fell down to about 1.1K after about a minute. I can live with that. I may be back if I have to do the hammer thing too often though.

Thanks to all!

Rich

tsuter · 02-26-2003, 05:24 AM

Good news. That means no one tampered with your Aux Air Sytem and the parts are correct. Just use parts drawing 1/7/3 for troubleshooting and remember that the locations of the AAV and DV are reversed. No big deal.
The AAR has a sliding half moon shaped metal gate. It slides across the hole in the AAR closing it off. So when cold, the hole is open. As it warms up the metal gate slides into the hole and slowly closes it. It is activated by the famous Bosch bimetallic strip down in the longer section of the AAR heated by a ceramic encased wire element and the motor itself.
When you stuck the screw driver in there it was open. If it was closd you would bump into the sliding gate. Be careful as it is sensitve. If you can spray cleaner in there then use the screwdriver to manually work the gate back and forth. You can only do this when it is fairly warmed up and mostly closed.
Souk says you can see in there with a mirror but I've never tried that I just take it off to clean as best possible.
Good luck.
There were probably a dozen other possibilities but this is straight forward one.

Rich Lambert · Rich Lambert's Garage

Does the half moon shaped gate slide from the bottom up?

Rich

tsuter · 02-26-2003, 07:45 AM

If you hold it in your hand and look in the side that has the metal hose attached i.e., air flow would be towards you see arrow on top, then the metal gate slides left to right across the hole to block it. It is activated by the bmetallic strip which is mountd inside the elangated portion and fixed by a metal plug at the end. Since this strip flexes left to right, that is the movement of the gate in the slot.

Superman · 02-26-2003, 10:18 AM

Like I said in a recent thread, I failed to listen to JW twice, and twice paid the price. Had you taked his advice on the hammer test, you would be days ahead.

Hey, as long as some CIS geniuses are at work here, I'd like to know how in the world my idle goes high when the engine is warmed up, and I've shut it off for a couple of minutes. It would seem unlikely that with all that heat, the AAR would open up. But I am experiencing this phenomenon. Engine warm...normal idle...shut it off for a few minutes and the idles goes high.

tsuter · 02-26-2003, 10:34 AM

What is the outside temp? I have seen this when it is pretty cold ambient. The AAR actually does start to open shortly after you shut down letting in a little air when you next start. The the 12V ceramic pig in blanket heater kicks in and closes it again fairly quick. Until you shut off again - no 12V - it starts to open again. So it is the ceramic heater working - not the heat transfer from the motor.
Lets not discuss adjusting the AAR!