Pressure Sensor, Air Slide

[oscar]

I think I found it.  This is a VW part.  This is an air slide valve for a 1980 to 8 Jetta.  The tubing fittings are a bit smaller than the mercedes but it will fit.  This part is electrically heated, not heated by cooling water jacket.  If you want to try this you'll need to fabricate a block-off plate to cover the hole left when the OEM part is removed.

Here's the part:

http://www.discountvdubparts.com/VW_Auxiliary~Air~Valve_list.html

That's interesting Steve,

I've seen those in online shops before when doing broad searches for aux air valves but I didn't know they're electrically operated.  Any idea how they work as far as what causes the valve to close?  I'd imagine rigging an inlet and outlet hose wouldn't be hard, making look pretty or hidden perhaps another challenge, but what wires plug into it and where do they go?

[UT_Tech]

There are 2 electrical terminals for a heating coil.  When current flows the coil heats up and the air passage slowly closes.  I think the best place to connect this is in parallel with the electical connector to the warmup regulator.

[oscar]

Hmm.  The d-jet doesn't have a warmup regulator and I'm not sure how they work, I don't know much about k-jet. 

That being the case, if the WUR is connected to the VW valve, does the WUR give off this current only once the engine has warmed up?  In other words, I'm assuming the VW electric valve closes quickly once current is applied to it, is that right?  If that's right, then I don't know how current could be applied to the VW valve in a d-jet setup only after the engine has neared or reached normal operating temp.  Unless perhaps a current is supplied thru the coolant temp switch which then closes a circuit once the coolant is warm enough.  Perhaps the vacated hole for the original air slide could be used for a dedicated coolant temp sensor switch.

[UT_Tech]

Oops, sorry..  I forgot you have D-jet.  That's the whole point of this exercise, isn't it?
I think the key to this conversion is keep it simple.  Wire the VW part to any +15 circuit
(hot when ignition on).  This will introduce a very small error because the time delay in the VW part
will start when the ignition turns on which is very shortly before the engine starts.
This should work fine.  The only way it would NOT work is if you turn on the ignition,
then wait a minute or two before starting then engine.

Steve

[Big_Richard]

I think I found it.  This is a VW part.  This is an air slide valve for a 1980 to 8 Jetta.  The tubing fittings are a bit smaller than the mercedes but it will fit.  This part is electrically heated, not heated by cooling water jacket.  If you want to try this you'll need to fabricate a block-off plate to cover the hole left when the OEM part is removed.

Here's the part:

http://www.discountvdubparts.com/VW_Auxiliary~Air~Valve_list.html

Heh, thats familiar, that exact auxillery air valve i held in my hands only a couple days ago. Its also used on euro 732i bmw's of that era.

[UT_Tech]

I think you're right.  As I recall the BMW 320i also used and air slide valve very similar to the
VW.

[Big_Richard]

I think you're right.  As I recall the BMW 320i also used and air slide valve very similar to the
VW.

Can you tell me any more about these bosch electronic auxiliary air valves ? Are they opened and closed by the ecu pending input from a coolant temperature sensor ? Or is there something much more primitive going on, such as the engine heat is used to open and close it, I noticed they are bolted directly to the cylinder head on bmw's.

[UT_Tech]

This is the primitive sort.  In the VW application the heater in
the air valve is energized by the same hot-when-engine-run circuit
which energizes the heating element in the warmup regulator. 
This part is used for VW CISand CIS-A applications, which may
be the same as BMW.  I believe the mountine is coincidental.  On a
VW this device is mounted a few inches behind the head just
underneath the intake plenum.

[SELfor50]

Oscar...

I removed the Air slide off my K-Jet (Ol'smokey) engine bout 4 weeks ago and water spewed out the top.  If i'm gonna remove it on Ol' silver how do i avoid this?
I just wanna check that it's functioning sweet.
Also does the K-jet have an MPS??  I seem to have the same as your 350 over on the right of my engine....  Just wondering if this needs checking as well.
My car doesn't necessarily cough when warmed up, but after being warm then turning off...if i start it again...it coughs hard until / unless i give it a pump of the pedal to get the revs functioning normal.
after that it idles ok..  But also when cold it idles pretty bloody high.

I guess main question is, how to remove the air slide on functioning engine without fluid spilling everywhere - and when i re-attach it do i need to use a sealant of some type??

Cam.

[oscar]

Coolant coming out of the hole when removing air valve  -  I don't reckon you can avoid it entirely because it seems like a low spot, but when I removed my valve there was a slight overflow not like what yours did.   Anyway, I think I minimised coolant coming out by releasing pressure from the system by loosening the rad cap on the expansion tank and I also worked on a cold engine.  That might make all the difference.


No MPS on the K-jet so rule that out.  I just had a look for some pics of ol smokey and I reckon what you might be looking at is the cruise control actuator.  It's the only thing I can think of that looks like an MPS but is much bigger.

Regarding the cough on a warm start up requiring pumps of the pedal - Personally I don't know but it sounds familiar like other k-jetters have complained about the same thing.  More likely a range of things to check but I'm going to guess and I mean guess, leaking injectors.  The fuel/air mix becomes too rich for a warm engine.  You know what, I'd post the problem up as a separate Q with any clues you got and see what suggestions come back.  If it was leaky injectors you'd get black smoke initially but.  I'll leave it there before I start making shit up.

[SELfor50]

Thanks for your help Oscar!! As always, muchly appreciated!

I'll give the air slide a go this weekend.

As for the cruise control actuator (and yes that's what i was referring to) I'm gonna look at removing it - doesn't work anyway and i'm thinking it'll be another thing that's lightening up Silver as well as possibly less strain on those horsies...

Will get mechanicals, and timing all done in the next week then i'll post a new topic with details of any remaining problems.
But i think you may be on the track with the injectors.
I can just un do those and pull them out for a clean right??

[brettj]

Oscar,

I bought a brand new air slide and installed it today. The antifreeze did spill out a bit from the engine block but was not a problem. The racing issue is gone and the car is running much better! Only problem now is that it keeps stalling! I think that the idle speed is set too low  as the rpms sit at 500. The  MB service manual states that the rpms should be between 700-800.What is the best way to adjust the idle speed? Do I move the control in the passenger compartment floor area or do I adjust the idle speed air screw next to the air slide? Also, the top hose of the air slide, do you need to clamp that hose on? My air slide hose never had any clamps on either end.

[UT_Tech]

The idle air speed screw will bring up the idle speed. 
I would put on hose clamps.  In theory it shouln't be needed
because these hoses are exposed only to vacuum, but
you never know....

[brettj]

Thanks UT TECH, will go right out and give it a try!

[oscar]

That's great news Brett and some confirmation there too how the idle speed screw is often set too low to compensate for a stuck open valve.  Remind me again why am I bothering with an old air slide

This probably sounds obvious but make sure the engine is at operating temp before you touch the idle screw.  Use a digital tach if possible to get an accurate rpm reading. 

Regarding hose clamps, mine had them before I bought my car, but I not long ago loosened them to see if I could notice any difference.  I haven't so far and I've been too lazy to remove them completely.  In the brochures you'll see the hoses without clamps, but in yesterdays thread by Andrew280sel about his 350, there's a classic case of a stretched loose vacuum hose causing trouble, in this particular case, with the Pressure Sensor.  I suppose in the end it comes down to how good your hoses are.

Oh and about the control in the passenger compartment footwell.  Are you referring to the knob that "clicks" on the ECU.  That controls the idle mixture but not rpm's as such.  It's primary function is to control carbon monoxide emission.