All of a sudden reving up and down when cold

[meltedpanda]

so what is the part that is cleaned - are is it both??, and removing AAV- coolant will leak?

[rowdie]

Originally Posted by GaryF

The idle screw restricts an air passage only, no water involved. The AAV is the bit sitting in the water.

And it isn't that hard to remove. Other than if the hoses on the tubes going to the throttle body are old and stuck. Not much coolant loss on a cold engine. Just wrap some rags around to catch the seepage.

The Idle screw might have carbon build up and is easy to clean. Screw in all the way counting the number of turns so you can put it back close. REmove, clean and reinstall.

[Graham]

Originally Posted by meltedpanda

when the screw is removed to clean , will coolant leak? or is it sealed in some fashion

The idle screw can be removed for cleaning, but somehow I doubt it will help much. It has a sort of rounded bullet nosed end. If it was dirty it would probably just have to be adjusted slightly differently.

The AAV is held on by 2 bolts - it sits on top of the block and the bulb penetrates into the coolant. It might be an idea to relieve the pressure on the rad first, but no coolant will leak out because everything else is below that level. It's a good idea to pick up a couple of gaskets first so you can remount it without leaks. I made my own out of some gasket paper.

I tried everything to get my AAV clean - soaked it in various solvents and detergents. Cycled it open and closed using boiling water and cold tap water. Sprayed Release-It and WD-40 into valve and let is sit overnight. I also squeezed the bulb a little so that valve would close more fully. It's a primitive device but I think mine now works properly.

You can get a good idea of whether AAV is leaking by if you squeeze the rubber elbow on the discharge side and cut off any flow (Engine speed reduces) You can also try disconnecting the elbow as in the picture and then put your thumb over the end of the rubber. That way you will get no air to idle valve and engine may stall if the idle screw is almost all the way in.

[meltedpanda]

Ok problem surfaced again , with no changes in temp or adjustments on my part. SO got out the trusty Ben Wilson publication on How to tune a Bossch FI system
I have read and re read the section on idle . I THINK I understand the procedure as follows - and thought Id see if any of you have done it this way

1) warm up engine to operating temp
2) remove air hose off of AAV , left side I am thinking , but not clear , the one that goes to the throttle plate, and plug - engine idle should remain the same - clearing the AAV as culprit. Or if idle drops replace or clean
3) completely close idle air pass ( adjustment screw) the idle at this point should barely keep car running, if it does not adjust throtle stop screw until lowest possible RPM is achieved to allow it to run
4)readjust the idle air pass to correct idle speed

Now then - I am unclear on the throtle stop screw, is that on the linkage? I am sure on mine that if I screw in the idle screw it will die, so adjusting the throtle linkage may be where I need to place my efforts - what do you all think
despite what Graham said , I have not removed the AAV and cleaned it , perhaps I shoud start there??

[Graham]

Originally Posted by meltedpanda

Ok problem surfaced again , with no changes in temp or adjustments on my part. SO got out the trusty Ben Wilson publication on How to tune a Bossch FI system
I have read and re read the section on idle . I THINK I understand the procedure as follows - and thought Id see if any of you have done it this way

1) warm up engine to operating temp
2) remove air hose off of AAV , left side I am thinking , but not clear , the one that goes to the throttle plate, and plug - engine idle should remain the same - clearing the AAV as culprit. Or if idle drops replace or clean
3) completely close idle air pass ( adjustment screw) the idle at this point should barely keep car running, if it does not adjust throtle stop screw until lowest possible RPM is achieved to allow it to run
4)readjust the idle air pass to correct idle speed

Now then - I am unclear on the throtle stop screw, is that on the linkage? I am sure on mine that if I screw in the idle screw it will die, so adjusting the throtle linkage may be where I need to place my efforts - what do you all think
despite what Graham said , I have not removed the AAV and cleaned it , perhaps I shoud start there??

Yes - you should probably clean and test it . You can prove to your self it needs doing by squeezing or plugging the outlet tube from the AAV when the engine is fully warmed up. (I bought a new elbow hose - it is flexible and easy to squeeze). If valve is closed when warm, idle should not change - Mine still changes speed, but not very much.

The stop they are talking about, is on the driver's side of the throttle housing - There is a section in the manual about adjusting the linkages that addresses this. I think it is basically just adjusted so the throttle plate is fully closed when you hit the stop. But I have not read that section for a while.

[meltedpanda]

so took it off, both 8MM bolts broke - still to be addressed
but the valve when hot closes, but not all the way??
cold it does open - full way
when hot should it close all the way not allowing air to pass at all or just restrcits it??
now onto the bolts-- 10 minute job - now several hours - you all know the story

[rowdie]

Ron,
That hurt clear in Oklahoma.

I must have run a full can of cleaner throught that valve before it stopped coming out black. Even filled it with ends corked at let it soak. I think it is supposed to close completely.

I have a '73 intake with a small crack near one of the mounting holes. I didn't waste time having it checked or repaired because I had the one off the '72.

[Graham]

Originally Posted by meltedpanda

so took it off, both 8MM bolts broke - still to be addressed
but the valve when hot closes, but not all the way??
cold it does open - full way
when hot should it close all the way not allowing air to pass at all or just restrcits it??
now onto the bolts-- 10 minute job - now several hours - you all know the story

I do know the story! - Just had my injectors out - 7 nuts came off the clamps just fine, but on one the stud came out. Went to re-install the stud, fumbled and the stud disappeared. Not on floor, nowhere to be seen. Bought one of those thin LED probes and looked down inside injector hole - Saw stud lying on top of inlet valve! Bought a small diam magnetic pick up and it came out first try! I had visions of removing head or intake manifold!

Some say the AAV does not completely close. But, I also read in one of the writes ups on the D-Jet system that the valve should be fully closed at 80C.

I tried to get mine to close. I must have cleaned it at least 3, maybe 6 times using ultrasonic, solvents, detergents. etc and each time, more crud came out. But the slide valve was still partly open in almost boiling water.

I then decided to risk it and squeeze the bulb. It is quite tough and I was able to create a shallow crease in it. I then retested and it did close a bit further. But, not having a spare, I left it at that.

When it is open, it is a vacuum leak. But you need some leakage anyway through the idle screw. If you still have some adjustment on the idle screw you are probably OK. If you can screw the idle screw all way in without stalling engine, then your AAV (or something else) is leaking.

I am no expert, but that is what I have learned from the forums and friendly mechanics!

barri (gurunutkins) has, I believe, replaced the AAV with an adjustable valve off a SAAB or Volvo. This allows you to open or close the valve using a switch on the dash. I want to do that one of these days.

[meltedpanda]

Originally Posted by Graham

Some say the AAV does not completely close. But, I also read in one of the writes ups on the D-Jet system that the valve should be fully closed at 80C.

well mine is close,which makes me think it should, I am going to let it soak tonight since I had to run and get a tap set ( a new one ) always need new tools
what was behind squeezing the bulb? This thing new is 400$ I dont have that kinda change so will skip that part
I may start a new thread on "who really knows if the AAV closes all the way when cold" what do you all think
Perhaps some friendly new parts guy could look for us

Old SL's - what better way to waste a saturday when your better half tells you she has "things for you to do"

[Graham]

Originally Posted by meltedpanda

what was behind squeezing the bulb?

It's a closed system - the fluid in the bulb expands and pushes the slide up to shut off the air. I think there is usually an indentation on the bulb where it was squeezed during manufacture to set the required travel. So if it is not going far enough and everything has been cleaned, it might need a little squeeze!

Once you have it back together and car is warm, try squeezing the outlet hose - When I do that, engine slows to a nice slow idle showing that there is still air leaking by.

[rowdie]

Did you manage to get the broken pieces drilled out? Good job. Pick up some anti-seize compound when you get the new tap set and bolts.

[meltedpanda]

got the broken pieces out ,too late to try the tap , but will tomorrow

[meltedpanda]

tapped and now with 10MM bolts, slight propblem is that I was a hair off so will have to enlarge hole slightly on AAV to match , make my own gasket and should be good to go. If anything , like almost always on these cars, you learn as you go.
I have decided to post the AAV question