VAP

<center><img src="http://pictureposter.audiworld.com/711/96_vacuum.jpg"></center><p>
I found a very strange issue that can be caused by plugging one little line that for the life of me I cannot figure out how or why. I finally threw my hands up and walked away from it in exasperation. I can easily understand why it will throw a code but I cannot understand how it keeps the EGR open slightly.

In the vac diagram above, the EGR solenoid line that should be connected to the air intake plenum or left open for the "EGR Mod" we've talked about here for years. I've marked that line with a "red X" in the above pic. We should all know by now that plugging or sealing that line will throw a code. But I found out today it will also open the EGR valve about 15-20% of it's normal fully open setting ALL THE TIME!! I just don't know "how" and may never understand. Unless perhaps on the outside chance of a faulty one-way valve or an internally leaking solenoid that's otherwise fine. Whatever it is it's weird and shouldn't happen.

Now it gets weirder. When testing it on an old IM with a mostly clogged EGR port nothing happens. It's goes mostly undetected because of the blockage. But if you take an IM that's just been through the IM Workshop or an IM that's otherwise just had it's EGR port cleaned your car will stumble, hesitate, cough, spit &amp; sputter at idle like pure crappola... IF it can idle at all! And you'll have somewhere in the neighborhood of 10 In Hg of intake manifold vacuum.

The root cause is our topic du jour... massive vacuum leak on a clean IM/EGR passage but only a very slight, imperceptable leak on a dirty clogged, mostly restricted IM/EGR passage.

My numbers show a car with a clean EGR passage would hover between EXCEEDINGLY bad idle to not idling at all. One thing you can take to the bank; if you suffered from this there would be absolutely NO question in your mind that something is terribly wrong! The only time it could be a light/subtle trait is if your EGR passage is mostly clogged. If it's clean the car would idle like luke-warm cah-cah if it idles at all.

I wish I understood how or why but again it's like a dog chasin a car...what would I do with it if I caught it!?! Just knowing this WILL happen if that line gets capped or sealed in this case is enough.

Lago Blue

<center><img src="http://i196.photobucket.com/albums/aa144/axe_360/vacroute.jpg"></center><p>The EGR Valve (EGRV) opens when vacuum signal is supplied to it's diaphram, via the EGR Solenoid aka Frequency Valve (F/V). That same vacuum is also trapped in that hard plastic brown line (see above diagram) between the EGRV and EGR F/V <i>unless it can be relieved</i>. This relief is <i>also</i> supplied by the EGR F/V. If not, the EGRV cannot close.

That relief (atmospheric pressure) is routed via the black line (see "EGR Vent Line" above) to the EGR F/V. The stock arrangement, over time, ends up being the cause of the EGRV being held open by trapped vacuum due to injested oily deposits drawn down that black tube and ruining (by contamination) the EGR F/V and/or plugging the inline "X" restictor, attached to the EGR F/V's Adjustable Vacuum Regulator. Either of these events will hold the EGRV open, <i>just like plugging that black line will.</i>

Your Intake manifold Change-Over Valve (the "N156") which is functionally interchageable with the EGR F/V (the "N18"), has a translucent vented (to atmosphere!) cap (see in diagram below) in place of the black line used in the same location, but on the EGR F/V. Plug that cap's vent and your I/M butterflies will stay open too.

<img src="http://pictureposter.audiworld.com/57225/vacuum_diagram_bulletin_in_color_website.jpg"><ul> <li><a href="https://forums.audiworld.com/12v/msgs/62638.phtml">for more see also...</a></li></ul>

VAP

indicated by the flow direction arrows in the diagram I posted? If so that goes a long way explaining things.

And if that is indeed the case it would benefit EGR solenoid vlave cleanliness &amp; longevity by pulling "clean/filtered" air from the airbox lid rather than the intake plenum or just leaving an open end in the engine bay somewhere to pull in airborne dirt, dust &amp; debris.

Reason I'm testing all this is to see how much more efficient the entire vacuum system can be made via small metering orifices in EVERY solenoid vacuum nipple, or adjustable valves off a centralized manifold, as well as a more direct, solenoid-free path to a larger capacity vacuum storage reservoir with a reservoir-dedicated one-way valve utilizing a 3-4 station solenoid-specific manifold array so that EVERY solenoid gets "metered" vacuum, based on need via the reservoir instead of from the intake manifold which can suffer from multi-parasitic vac loss if too many sources cyle at once thru a more centralized and sensible vacuum distribution system that relies on "stored" vacuum reserves rather than intake manifold vacuum. Vacuum brake-assist could be a part of this or left to it's dedicated vacuum source.

Basically an effort to make order from what has been up to now "vacuum plumbing chaos" accompanied by a more efficiently metered and individual solenoid adjustable vacuum delivery system. A vacuum distribution system that is small, centrally located, highly accessible with solenoid-specific colored silicone hoses that's a wiz to understand "at-a-glance" or adjust.

Lago Blue

<center><img src="http://pictureposter.audiworld.com/57225/3_knock_off_end_plate.jpg"></center><p>
...The Noise Damper to EGR F/V (N18) hard black plastic line routes atmospheric pressure to the EGR F/V where it is standing by, waiting for the F/V to return to it's default (un-powered) position. With power removed from the EGR F/V, it is spring loaded (see above) to open the atmosheric port, and (woosh!) the vacuum is relieved or neutralized and the EGRV is allowed to close.

The EGR F/V has two positions (one for each of it's functions):

- Un-powered: atmospheric is routed to the EGRV (EGRV closes); and
- Powered: vacuum is routed to the EGRV (EGRV opens).

<img src="http://pictureposter.audiworld.com/57225/5_blue_silicone_seal_out_of_position.jpg">

The EGR F/V -must- seal off the the vacuum or the atmospheric in whichever of it's two positions it is in. That is why it is so suseptible to contamination. The EGR F/V above was damaged by oil ingestion. It lost it's ability to effectively seal the vacuum port off -from- the atmospheric one.

Perhaps millions of vehicles have an air filter dedicated -just- for the atmospheric port of the EGR F/V (I used the vented cap from the I/M C/O Solenoid (N156)). Below is the EGR F/V from a Ford Windstar IIRC.

<img src="http://www.shockley.net/images/egr-solenoid-2.jpg">

The marshmallow sized filter is under that round gray plastic cover.

<img src="http://rockledge.home.comcast.net/RangerPictureGallery/EVR_EGR.gif">

What could possibly be confusing about this (below?

<img src="http://pictureposter.audiworld.com/57225/egr_solenoid_vacuum_hose_routing_email.jpg">

Under that sealant in the centre of black hour-glass shape (photo above) of the EGR F/V Vacuum Regulator is an adjusting screw. I have used this to minimize the vacuum used to open the EGRV. I've adjusted such that my CEL comes on briefly every time I'm just loafing along from a cold start (see link below).

WRT minimizing the vacuum services; I think you are absolutely correct in pursuing this idea as I found that the amount of vacuum required to operate my EGRV was way less than what it was originally being supplied with. Everyone's EGRV may have a slightly different requirement, determining what that might be is really quite simple, here, in part, is what I did:

https://forums.audiworld.com/12v/msgs/62046.phtml

For those of us with 90's, perhaps moving the I/M C/O Solenoid (N156) nearer to the actuator and the vacuum source might also prove helpful?<ul><li><a href="https://forums.audiworld.com/12v/msgs/62639.phtml">further EGR F/V Vacuum Regulator adjusting to minimum info...</a></li></ul>

moribundman

Here is the revised diagram:

<img src="http://pictureposter.audiworld.com/50038/96_vacuum_revised.jpg">

Luxus Panzer

Put a revision date on that so it is not confused with the old incorrect version in the future.

moribundman

The problem is, the old file is "out there." It's like the proverbial genie that won't go back in the bottle, no matter what I do to the original file that's uploaded on Audiworld. Even if I delete the old file, it will pop back up again, because people have copied the image and might reuse it. I can point folks to the right file nine ways until Never-Never Day, and somehow someone will still end up with the wrong file. :-P

If you care to actually look into my picture poster, you will notice that I changed the old file, which is now pointing people at the new, updated diagram:


Old, edited file in my picture poster:
<img src="http://pictureposter.audiworld.com/50038/96_vacuum.jpg">

Shiny, new file in my picture poster:
<img src="http://pictureposter.audiworld.com/50038/96_vacuum_revised.jpg">

Luxus Panzer

I would include a revision date and a denote that it is the second version on the new one. Easy way for newbs to distinguish the difference.

moribundman

I have the updated and dated September 2008 new diagram up, and I am also leaving up the old and marked as "old &amp; faulty" one pointing to the updated diagram. If that's too complicated and confusing, I just don't care.

I am certainly not going to attempt tracking down all the copies of the old diagram that people may have saved and still use.

If you would like to date the diagrams in a more elaborate and clearer manner, feel free to do so.

Luxus Panzer

<a href="http://s4.photobucket.com/albums/y145/pharoah007/?action=view&current=96_vacuum_revisedcopy.jpg" target="_blank"><img src="http://i4.photobucket.com/albums/y145/pharoah007/96_vacuum_revisedcopy.jpg" border="0" alt="Photobucket"></a>