Hey there, thanks for taking a look at my post.

My question is about two electrical/mechanical (insert term here: valves/solenoids/?) that each have a vacuum line running in and out of them at the rear of my engine. They are mounted at the rear driver's side of the valve-cover (4.9L, but I've seen them on the V-8's, too).

Apparently either the vacuum controls the flow of electricity, or the electricity controls the flow of vacuum - beyond that lies my questions.

What are they, what do they control, and how?

Then, more importantly, what are the engine-running symptoms if they go bad (electrically - not vacuum-leak bad)?

Let me just say I'll be seriously impressed with the person or people who know this kind of stuff!

Thanks.

 

Check out the Vaccumn diagram on the radiator core support. It will usally tell you what they are called. They you can try to figure out what they do.
Good luck

 

My 4.9 has three of them they are an EVR, TAD and TAB. The EVR solenoid goes to the EGR valve. The TAD and the TAB go to the vacuum controlled diverter valve that is on the discharge of the smog pump. This valve diverts the air from the pump either to the exhaust manifold or to the catalytic converter. The vacuum source to these solenoids comes directly from your vacuum tree via the vacuum reservoir.

 

[updated:LAST EDITED ON 26-Apr-02 AT 06:54 PM (EST)]Very impressive, mantta! I'd buy you a beer if you were here.

I have three also, but one is a little larger, or different looking, than the other ttwo, so I thought I'd leave that one out of the description for simplicity's sake.

I wonder if there would be any advantage to simplify the vacuum system to make the smog pump pump into only the manifold or the converter?

I guess as far as driveability goes with the straight sixes, the only one out of the three that a driver would notice a difference in would be if the EVR solenoid were going, or went, bad (I know this because I realized how much of an effect the EGR had on my driveability after I created a restrictor plate for it).

Maybe I'll play with the EVR vacuum tubes a little bit just to see what happens.

Thanks!:7

 

Let me tell you what I did on my 4.9. We have no emissions tests here so I put in a restricter plate like you did. I kept the smog pump operational and it discharges directly into the cat convertor. I removed the plastic diverting valve and the bracket that it sits on, so it don't look like something should be there. On the six tubes that go into each exhaust port I put in flare blanks (5/16"). I got them from a local refrigeration parts distributor. I then screwed the nuts back in that were on the six outlet manifold, and, low and behold, no leaks at all!! Oh, the vacuum source that goes to the EVR, TAD and TAB has been disconnected and capped off. I have a short bed truck with 3.55 gears and an AOD, and, on the highway I get 20-21 MPG. These flare caps I mentioned are made of copper, they are meant to go into a tubing flare nut to use it as a cap on a flare fitting.

 

That was sure a information-packed paragraph there, mantta... thanks, but mind if I try to get your ideas straight here?

1.) Ok, so first I take it you change the vacuum routing in some way to make the pump blow only into the converter? How was this done?

2.) Then you blocked off the ports with (? I'd like to see a picture of those "flare blanks (5/16")" you used) for what reason?

3.) Lastly, if you did not entirely restrict the EGR flow with the restrictor plate (you may have, but I couldn't tell from your post), what was the end effect of bypassing (I'm taking it that's what you did) the EVR to put the now-straight vacuum hose on the EGR? DOes this keep the EGR valve open or closed the whole time?

Thanks again.

 

In answer to your questions,
1) I completely removed the plastic diverter valve, and the discharge of the smog pump goes directly into the tube that goes to the catalytic convertor. I just used the same hose that went from the smog pump to the valve.
2) These flare caps look like a hat with the brim all the way around, they fit into a flare nut fitting. The ones in the cylinder head are flare fittings. If you look on the right side (pass side) of the engine you will see this tube that runs the length of the engine with a branch going into each exhaust port. These branches that go into the cylinder head are what I blocked off. You could just as easy cap off the whole manifold where the check valve is on the inlet, but, it then looks like something is supposed to be there. Removing that manifold and plugging them six holes is a big job because you have to remove the upper intake manifold to do it, and them them lines that go into the head are very tight. I would just cap off the manifold if I had to do it again.
3)I totally have the EGR blocked off with the restrictor plate. That alone gave me better acceleration and overall better performance.

I would take you up on that beer but, I had to give it up, I had a liver transplant two years ago.
Have fun, you will be surprised what that 4.9 can do!!