Lazy AAR??

[Dave27S]

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Hello all.

First of all Merry Christmas and a happy new year.

During the summer i had my 1976 2.7 CIS setup lovely and running better than ever. He's parked up for the winter but i start him once a week to warm him up.

Anyway it seems lately that during warm up he hesitates and pops back through the pop off valve coming off idle. When warm it settles down a bit. I checked all my fuel pressures, checked for air leaks, Co2 level etc. Currently the only thing i may have found is with the AAR.

When cold, (approx 5 degrees C) the AAR is half closed. After 20 mins of running the engine, the AAR goes to a 3/4 closed. I expected the AAR to fully close within 10 mins or so??? ive checked the resistance and its 34 ohms. The AAR is also getting 12V with the engine on.

i havent yet warmed him up and blocked off the AAR to see what happens but i presume my mixture will be out the window?

I'd appreciate any input. had alook through the search function and found some stuff on opening the AAR and repairing the element....

Thanks,
Dave

[T77911S]

the AAR only effects idle, not mixture or how the car runs. if you have not noticed a change in idle, then the AAR is operating as it always has.

check for vacuum at the WUR.

check for vacuum to the retard? at the dizzy, make sure it is not there as soon as you open the throttle.

check timing and advance. this will also check the retard. make sure timing advances as RPM's increase.

how old are the diist cap, rotor and plugs?


what is the co? post all your pressure results. CCP, WCP and system.

[john walker's workshop]

too lean when cold is my guess. first adjust the hot running CO up to about 3.5% and see if that helps enough. if not, do a search for adjustable warmup regulator. that pin needs to be moved down just a few thousandths to richen the cold running mixture and get rid of the popping.

[Dave27S]

Hi, thanks for the swift response.

The cap, rotor and plugs were changed in the summer along with a new coil and ignitor 2 pickup. The vacuum retarrd was removed and timing is set at 5 degrees BTDC at 900 rpm and opens to 35 at 6000K.

The FD and WUR were also overhauled in the summer with system pressure at 75psi, CCP at 22 psi and rises to 44psi WCP. The WUR has two vacuum lines attached with no leaks apparent.

I have an O2 sensor installed that fluctuates between 400 and 800 mV at idle and is fairly steady at 750 mV when rpm is held above idle.

Currently when cold if i open the thrrottle too quickley the engine will hesitate and sometimes pop from the pop off valve before reving. If i open it slowly its fine. once off idle it will rev happily with no problems. Once warm this problem is significantly reduced. From the o2 sensor readings i thought im already into the richer side of the mixture scale.

just throught that with my AAR not closing fully that im adjusting the mixture and bypass screw to accomodate?

Thanks

[T77911S]

check the vac to the WUR. one is vac to lean out the mixture. at WOT it is not there to richen the mixture, but, when you first open the throttle, the vac will drop making it richer just for a split second. it kinda acts like an accelerator pump on a carb. one way to check it is see if the CP drops when it is removed.

the other connection is just to atmosphere.

[Dave27S]

Thanks, ill check to see if it drops the CP when removed. Below is how the lines are currently attached from the WUR to the throttle body. different sized hoses:

[T77911S]

my WUR vac goes to the rear of the TB. i believe it needs to be below the throttle plate, or just below it, so it has vac all the time until you go WOT. my vac retard to the diist was connected to the front, i think it would be the bottom one you have marked, but i have also changed my TB to a bigger one off of a 3.0.

[john walker's workshop]

22# CCP is usually too high (lean). may be ok in the summer, but not in the winter. get it down to 15#.

[Gunter]

Dave27S:

We have some experience with Winter Storage here in Canada.

My suggestion:

DO NOT start your 911 for Winter Storage. Instead, disconnect the Bosch CDI ignition module and remove the fuel pump relay (Or fuse). Then just crank the engine for a few turns to let the oil pump pressurize and lube the engine once a month.

For storage, I change oil, fill the tank, add Stabil plus Injection Cleaner and run it through the CIS. After that, I only crank the engine a few times during Winter without ignition and fuel.

I made a special stand with a 150W bulb on the passenger side floor and put a couple old comforters over the 911.

To check and adjust your CIS, wait for Spring.
If the AAR is suspect, it may be just sticky??

Check the AAR located on the right side of the engine between 5-6 intake runner.
It's the item that has a small electric plug and a large vacuum hose connected to it.
Open the clamp holding the outside-hose.
Pry it off with the screwdriver just enough to get it out of the way so you can see into the opening.
Don’t worry about the Alu pipe; it’ll move enough.
With the help of a small mirror and a light, peek inside the AAR.
When COLD, you should see an opening in the slide shaped like a half-moon.
When HOT, the opening was completely closed on mine.
If it isn't closed, the AAR is either kaput or doesn't get any power.
You can spray some WD-40 into the valve in case it is just sticky.
To check the power, carefully open the tiny clip on the plug with a very small screwdriver and pull it off.
The wire clip is tricky but necessary; don't yank it off.
Start the engine and check the plug for 12 V.
Just ignition ON will not get power to AAR or WUR; engine has to run.
(One wire is power, the other (brown) is ground)
With power to the AAR, it should close after about 5 minutes.
If all is well, replace the hose and clamp securely.

To make the WUR adjustable:



I modified a couple WUR's like that but I didn't add the small dowel pin because I don't believe the plug will rotate during adjustments.

[Dave27S]

Thanks Gunter, sounds like you get some serious winters up there!

i peeped into the AAR and it never closes, 3/4's at the most at 20 mins of engine running. ill see if i can free him up a bit!

[john walker's workshop]

that isn't the problem. and the air regulators never completely close FYI.

[Gunter]

Good tip, JW.
Mine did close completely when checking it during Summer-drives.
Has air temperature something to do with amount of closing?

Some people have repaired the AAR by opening them and then tweek the mechanism etc.

I believe the '76 has an adjustable Deceleration Valve?
And AAV?
If you have, I assume you have checked for vacuum leaks on the lines and hoses for WUR, AAR, AAV and Decel. Valve?

The reason that I don't believe in starting the engine in Winter is that it really doesn't get hot enough and lubing the engine can be done by just cranking without ignition and fuel.

Battery is on a 1A-maintainer, of course.

[boyt911sc]

Originally Posted by john walker's workshop

that isn't the problem. and the air regulators never completely close FYI.

JW,

It is not that easy to contradict the expert's opinion because you are a highly respected and I'm also an ardent admirer of yours. Since this is a technical forum, judgement should be based on facts or data. Subsequently, since I have spent some time investigating several CIS components like WUR's and AAR's, I don't believe your above statement could hold water.

To prove my point, I measured the time elapsed to close the valve completely after applying 12 volts to the heater. I've performed similar tests several months ago but wanted to repeat for demonstration.



Sample #1..........AAR (0-280-140-204).............completely closed after 5.0 mins.
Sample #2..........AAR (0-280-140-209).............completely closed after 4.5 mins.
Sample #3..........AAR (0-280-140-209).............completely closed after 4.2 mins.
Sample #4..........AAR (0-280-140-218).............completely closed after 6.0 mins.
Sample #5..........AAR (0-280-140-218).............completely closed after 5.5 mins.

The value of the heating resistance (Ohms) has a direct correlation to the closing time (elapsed time) provided there is no obstruction to the valve. These AAR's are intact and have not been altered or molested. They came from different members who decided to get rid of their CIS and go to other systems. I'm no CIS expert but these data clearly show that AAR that does not fully close is somewhat 'defective' or questionable. Would someone comment on these data? Thanks.

Tony

[mca]

Tony ... now we all know where to come get our CIS parts when we need them .

Nice work btw. Following this for educational purposes.

[Vin-barrett]

I did the same test as Tony just a week ago (I only have three AAR's though) which got similar results all 3 were around 5 minutes for the door to close all the way...

That said what I'm pretty sure JW means by doesn't fully close is that air always passes through it even if the door is fully closed. It can only reduce the air going through it, not stop it completely.

[Dave27S]

So it sounds like my AAR is on the way out then? Still 1/4 open after 20 mins!

Now maybe i have basic idle setup issues also but it could be worht my while replacing the AAR before i do anything else....

Thanks for the test results!

[T77911S]

i thought his problem was popping off idle, = lean. ?? as i said and JW said, not the AAR.
either something with the vac to the WUR or an air leak. 22 psi CCP? check the spec. check the popoff valve, make sure it is seated properly.


tony, you either need a woman are incapable of wooing said woman ( pirates of the carrabean). i am always amazed at what youcome up with.
i dont think my AAR has ever kept the idle up 4.5 min. 2-3, maybe. even at 30deg this morning. i did not think they completely closed either, although i never really messed with them that much so i am open to learning more about them. i always figured with the throttle plate closed, there was not enough around the idle circuit, so it needed a little extra from the AAR to idle.

[Gunter]

Originally Posted by Dave27S

So it sounds like my AAR is on the way out then? Still 1/4 open after 20 mins!

Now maybe i have basic idle setup issues also but it could be worht my while replacing the AAR before i do anything else....

Thanks for the test results!

What would Plato do?

Remove the AAR, open it and see why the slide-valve doesn't close all the way.
I opened one by carefully grinding the rivets off and then used screws to close it after inspection. To test the AAR, I keep an extra plug with short leads, supply 12V and watch for about 5 Minutes.

Before anything else, I'd remedy the AAR-issue first. Adjusting mixture etc. would only make sense after any unwanted vacuum or air is eliminated.

Do you have a fixed AAV and an adjustable Deceleration Valve on a '76?

[ossiblue]

Originally Posted by Dave27S

Hi, thanks for the swift response.

The cap, rotor and plugs were changed in the summer along with a new coil and ignitor 2 pickup. The vacuum retarrd was removed and timing is set at 5 degrees BTDC at 900 rpm and opens to 35 at 6000K.

The FD and WUR were also overhauled in the summer with system pressure at 75psi, CCP at 22 psi and rises to 44psi WCP. The WUR has two vacuum lines attached with no leaks apparent.

I have an O2 sensor installed that fluctuates between 400 and 800 mV at idle and is fairly steady at 750 mV when rpm is held above idle.

Currently when cold if i open the thrrottle too quickley the engine will hesitate and sometimes pop from the pop off valve before reving. If i open it slowly its fine. once off idle it will rev happily with no problems. Once warm this problem is significantly reduced. From the o2 sensor readings i thought im already into the richer side of the mixture scale.

just throught that with my AAR not closing fully that im adjusting the mixture and bypass screw to accomodate?

Thanks

Back to the problem. You appear to have a lean cold start condition. It is not clear from your post if the fuel pressures you mention were for the current, very cold, ambient temperatures. Summer temps may justify CCP of 22psi, but 5*C does not. In my very limited experience with CIS, I have found the first and easiest step is to confirm fuel pressures, using the appropriate ambient temp tables.

The AAR may or not be an issue since warm running is good and can be further investigated after proper setting of fuel pressures, IMO.

[BRP83SC]

Originally Posted by Gunter

Dave27S:

We have some experience with Winter Storage here in Canada.

My suggestion:

DO NOT start your 911 for Winter Storage. Instead, disconnect the Bosch CDI ignition module and remove the fuel pump relay (Or fuse). Then just crank the engine for a few turns to let the oil pump pressurize and lube the engine once a month.

For storage, I change oil, fill the tank, add Stabil plus Injection Cleaner and run it through the CIS. After that, I only crank the engine a few times during Winter without ignition and fuel.

I made a special stand with a 150W bulb on the passenger side floor and put a couple old comforters over the 911.

To check and adjust your CIS, wait for Spring.
If the AAR is suspect, it may be just sticky??

Check the AAR located on the right side of the engine between 5-6 intake runner.
It's the item that has a small electric plug and a large vacuum hose connected to it.
Open the clamp holding the outside-hose.
Pry it off with the screwdriver just enough to get it out of the way so you can see into the opening.
Don’t worry about the Alu pipe; it’ll move enough.
With the help of a small mirror and a light, peek inside the AAR.
When COLD, you should see an opening in the slide shaped like a half-moon.
When HOT, the opening was completely closed on mine.
If it isn't closed, the AAR is either kaput or doesn't get any power.
You can spray some WD-40 into the valve in case it is just sticky.
To check the power, carefully open the tiny clip on the plug with a very small screwdriver and pull it off.
The wire clip is tricky but necessary; don't yank it off.
Start the engine and check the plug for 12 V.
Just ignition ON will not get power to AAR or WUR; engine has to run.
(One wire is power, the other (brown) is ground)
With power to the AAR, it should close after about 5 minutes.
If all is well, replace the hose and clamp securely.

To make the WUR adjustable:



I modified a couple WUR's like that but I didn't add the small dowel pin because I don't believe the plug will rotate during adjustments.

Gunter, Does the aar get its power from the fuel pump relay?