Auxillary air valve

Hi, new on the forum. Thanks for all wonderful information, impressingly.

Back and forth i´m working on my Mercedes w114 280e. The car has not been started for 30 years and yes even Bosch quality affect some of the components in the fuel injection. My idle is sawing, exactly like in the film of the 350 in chapter 9. And of course the auxillary air valve was stucked in open position. Happily i found a new one and switched. But the problem remains.

What could it be beyond the auxillary air valve. And if it is the auxillary air valve, wouldnt idle be good when engine is cold because mine is sawing at any engine temperatur??

Kind regards! Mikael

Hi Mikael,

well any false air into manifold can cause the sawing in idle-run. So just to make sure:

1. You only have sawing when throttle is closed, no foot on pedal?
2. You did the test with closing the air hose to intake manifold?

Please do no throw the hanging AAV away. I could use it and repair it for myself if you don't need it.

Hi, thanks for fast answer, and:
1 Yes only on idle, no foot on pedal.
2 Sorry, I´m not following you on what air hose should be closed?

Yes i understand that all D-jetronic parts should be kept, even if they are broken:)

Kind regards Mikael

Hi Mikael,

there is one hose from air filter to AAV and one from AAV to intake manifold. Close the second one by squeezing it on warm engine. If rpm changes by more than 100/min, your AAV is still open. If it is closed you will hardly notice a difference.

Hi!
Thanks for quick ansvers, there has been some other things that caught my attention but now im back
Things I´we done:
I ran the engine hot and disconnected the hose after the throttle
attached to intake manifold and i had no difference in idle-sawing, the RPM were not changing so i beleve the new one works.
I disconnected the hose between intake manifold and MAP-sensor and i still had the idle-sawing.
I have put in a new airfilter.
The wacuum is pendling between 200-300 mm-Hg. Measured on Connection to central locking.
So, luckely i have some parts to switch with but not an entire functioning car. The engine runs verry good except for the idle.
What i notice is a short delay if I accelerate a bit slow and that the spark pluggs are verry sooty. I have not tested for vacuum leaks with starting fluid...

Happy New Year! Kind regards Mikael

Hi Mikael,

when I read what you did I have the impression that you created additional false air by opening hoses to intake manifold instead of closing them. Maybe I misunderstand you.

So again: Please squeeze and close the hose from AAV to intake manifold. If that lets rpm drop by more than 100 rpm and sawing vanishes, then it is the AAV leaking. If not, you have another leakage. Measuring vacuum on central locking is not a good idea. Use a T-connector and measure it on MAP sensor hose while MAP sensor is still connected. If you disconnect MAP sensor, it will leak air to intake manifold there.

Hi!
My bad, I always block any hose when I open for testing something. Think I have understood and folloved your information

So you think there might be a leakage after all.
But if you have this idle-sawing showed on the video could one say that´s caused by to much or to little vaccum in the manifold.

So, now there are some things to check tomorrow as well

Kind regards Mikael

Too little vacuum. Leakage means that the engine sucks air into cylinders, throttle is closed and air comes in through other ways.