Mystery valve

[Henrik]

I just installed a reconditioned 3.3i engine (1978) with L-jet in my e9. After a lot of hassle I managed to start the engine. The problem now is that it has too high idle. Idle speed is between 1800-2000 rpm. I try to lower the speed by adjusting the throttle bypass screw, but it has no effect whatever position it´s in! The only thing that helps is turning the distributor, but that´s not the right medicine. I also checked all the hoses on the intake manifold to see if it gets false air. Throttle body and throttle switch are also adjusted. After searching on the web I found out that on the old L-jet system it´s possible to adjust ignition?? and idle with a large brass screw that sits in an aluminum tube (picture). This I found at the bottom of a box of old parts. The problem now is where to put it? Has someone experience with this?

Henrik

 

[decoupe]

I lost one of these at a Led Zeppelin concert in 1969.

 

[Bwana]

I lost one of these at a Led Zeppelin concert in 1969.

:lol: :lol: :lol: :lol:

Lost mine at Pink Floyd in El Lay in '74

 

[tmason]

Seen RS,LZ,Rush and the Who over the years but PF was hands down the Best Ever!

 

[Stevehose]

We didn't need one at Bob Marley at the Apollo theater in '80 - the audience passed them around to one another.

:lol: :lol: :lol: :lol:

Lost mine at Pink Floyd in El Lay in '74

 

[decoupe]

Henrik:

Sorry about the humour - I've looked a every diagram/schematic/pictures for the L Jet I could find and this thing doesn't show.

Symptoms sound like fast idle that won't kick down. The idle screw gives some control to the volume of air but if that has had no effect then I wonder if the Auxiliary Air Valve is the culprit. Can it stick open and is just dumping air into the throttle body?

Doug

 

[pamp]

Doug,
You are the L jet guy....if this was D jet I would have said the same....Aux. air valve not functioning properly. Does the L jet a use similar valve? On D jet it is mechanical, the L electrical? So the valve of mystery isn't but should be part #2 in this diagram? http://www.penskeparts.com/DiagramsMain.aspx?vid=47164&rnd=03192010 Then go to fuel preparation...."additional air valve"

 

[decoupe]

Henrik:

Have a look at the Technical FAQ page on http://www.firstfives.org/ and click on the Aux Air Valve FAQ article. It says the Aux Air Valve pre 1979 is prone to sticking so if you have one that may be the culprit.

Doesn't answer your "what's this" question....

Doug

 

[pamp]

So I was more or less correct....just need to know the set up this gent has....the valve of mystery would work nice on my still.....no weed for me!

 

[Henrik]

I wonder if the mystery valve may be a part of a winterization device, installed in 733i produced for Northern Europa. Attached picture shows another mystery "thing". It was mounted between the air filter and the Air Flow Meter. I guess it was designed to supply hot air from the top of the exhaust manifold to the Air Flow Meter inlet, and the mystery valve was there (in the hose from manifold to adjust the hot air flow). So I think the Valve has nothing to do with idle adjustment at all (not on a late 78 model)

As you two point out, the Aux Air Valve may be a unreliable, but I blinded off the inlet and outlet to see if it helped, but the idle was unaffected, so I don´t think it´s the source to my problems.

After a lot of investigation I discovered that the underneath the AFM it´s an Idle Mixture Adjusting Screw (picture), so my next move is to check if this can be the right medicine.

 

[Luis A.]

After a lot of investigation I discovered that the underneath the AFM it´s an Idle Mixture Adjusting Screw (picture), so my next move is to check if this can be the right medicine.

Yes, that is the screw I would have adjusted (in the 3rd picture). Which one were you adjusting before, which you referenced in your first post? I have not yet adjusted my L Jet but will be doing that in the next month or two so I might add to this then.

 

[Henrik]

Hi!
I adjusted the throttle screw from end to end and nothing happened!
Right now I try to repair an oil leak between the oil sump and the engine block, so I haven´t been able to start up and see if the AFM bypass screw will change anything. What a strange position for an adjusting screw. How is it possible to operate it while AFM is connected to the throttle house?