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Sat Aug 01, 2015 10:13 am

My 73 412 Wagon (auto trans) has no sign of any type of electromagnetic decel valve anywhere. Could this be correct or was it removed at some point during its life? Thanks

Sat Aug 01, 2015 10:41 am

The decel valve is generally mounted on the bracket with, or near the MPS. If it had one....it will also have a pressure switch on thr transmission.

Many of them are removed by owners and mechanics who dont know what they are...or because they give problems and the owner or mechanic doesnt know how to adjust or repair it.

If you remove it...it can generally be adjusted around with some work. Yours is D-Jet right?

Sat Aug 01, 2015 12:46 pm

Yes, D-Jet. What is odd is that the diagram shows a port on the left side of the plenum that says 'Brown' and leads to either an electromagnetic or mechanical decel valve:

I don't have that port on my Plenum:

So, I'm at a loss as to how to hook this up if I had one.

I do have a port on the throttle body here, and have no clue what goes here:

One final question. The vacuum throttle thing seems out of adjustment. It doesnt touch the throttle at all, and when you apply vacuum to it, it only pulls further away from throttle:

Is there a thread on how to adjust this? Thanks, I'm getting close thanks to to this forum, especially Ray G. !

Sat Aug 01, 2015 1:09 pm

Its also possible it had a manual/vacuum decel valve. Dont believe what the books say (what little they do say).

Not all automatics came with the electronic decel valve. My very first car was a 1972 411 four door with auotmatic. No electronic decel valve.... and it had 55k original miles on it and was complete.
I cant for the life of me remember a decel valve at all. But if it had one it was vacuum.

I had 1973 412 wagon, a 1973 412 four door and a 1972 411 wagon.....none had the electronic valve. The 411 had nothing but the four had the vacuum decel valve. All of those were auto until I converted them to manual.

So....if you find no pressure switch on the transmission. ....just put in a manual decel valve. Ray

Sat Aug 01, 2015 5:11 pm

Thanks Ray! Any idea how to adjust that throttle positioner thing above?

Sat Aug 01, 2015 6:19 pm

ClassicCamper wrote: Thanks Ray! Any idea how to adjust that throttle positioner thing above?

You can only do it while its running. If memory serves its in the Haynes manual.....or at least a diagram showing the gap is.

The object is to have a specific gap between the throttle lever and the end of the bolt at correct stable idle speed...with the throttle all the way closed.

When you rev up to say...1500 rpm or so...and drop the throttle lever....when the throttle lever return to closed...you should see that in that second or so....there is no longer a gap between the bolt and the throttle lever.

So in other words.....as you speed up...you will see some increase in vacuum and the throttle kicker bolt will be seen to move back just slightly..increasing the gap between the throttle lever.

Its deceptive...because the throttle lever is moving away from the bolt...but the bolt is also moving away from the throttle lever......and if you keep your eye on the bolt...it will slowly move back toward where the throttle lever will be when the throttle is closed......dont worry about that...just telling you what to expect.

But when you release the throttle.....when it comes back to "0" or closed....if the throttle kicker is properly adjusted.....it will have moved CLOSER to the throttle lever.....than the position it was at idle. :wink: and in about 1.5 seconds...you will see the kicker bolt...retract and pull away from the throttle lever...allowing it to close properly.

The object is that....the throttle kicker is technically a spring loaded controlled vacuum leak. When the throttle is closed....vacuum is highest. The kicker retracts far enough that there is a gap between the bolt and throttle lever.

Open the throttle...vacuum drops...and the spring drives the throttle kicker bolt forward.
Hopefully.....if the throttle kicker is adjusted correctly....meaning the bolt adjustment and locknut is not extended too far or the spring tension too high....the throttle kicker bolt will not strike the throttle lever.

As rpm climbs...you will see vacuum retract the throttle kicker somewhat....but because vacuum never really reaches idle level again until the throttle is fully closed....the position the kicker bolt is in...will contact the throttle lever and prevent it from closing all the way as it snaps shut.

This position...is where you want the bolt to be. If its too far out....it stops the throttle from closing ...and leaves it with too much opening. Too little and it doesn't help.

So......you Snap the throttle closed....and the throttle lever hits the kicker bolt....and because the throttle opening is greatly reduced....vacuum climbs fast...pulling the kicker bolt backwards and smoothly allowing the throttle to close the last few millimeters.

The object is to prevent the engine rpm from going all the way to idle so fast that the torque converter has not had time to bleed pressure off and disengage from its hydrostatic lock between trans and engine.

So if idle is say....850....the kicker bolt probably arrests throttle closing at about 950-1000 rpm and drops it off over about 1.0-1.5 seconds.

You will know when its not right because the torque converter will keep dragging the engine rpm down to about 500 when the throttle snaps close threatening to stall...if not actually stall...the engine.

There are two adjustments on the unit...kind of.... really you should not have so screw with the spring. It should be kind of locked in placed...but it can be adjusted.
I will look in the book to find the gap between bolt and throttle lever and post later.

Also....the vacuum nipple it connects to on the plenum...should ...if you look in the end of it...have a pressed or welded in restriction with a small hole drilled into it. This is to delay vacuum build up.

Also you can Tee the decel valve into the MPS port. Its the MPS it actually acts on anyway. Ray