Thermal vacuum switch
 

On my '83 Eldorado, I get no vacuum going to the EGR valve. Checked with a vacuum gauge teed from the line going into the EGR and watched while driving about 10 miles. (OK, I watched the road most of the time, but checked the gauge during times when I would have thought the EGR would have been active...during acceleration, etc.) I traced back to the TVS...one port gave me 20" of vacuum, the EGR/canister port made the gauge needle barely move. Before I run out and buy a new TVS, is this normal? I've looked, but nothing I've seen so far will confirm that it is or is not. In my experience, EGR valves usually have very low vacuum signals going to them, but THAT low?

Anybody had any experience with this item? My books seem to be silent on the subject...

Well, it appears I have fixed the problem. Turns out that the TVS port which normally runs to the EGR solenoid wasn't putting out enough vacuum. I ran a tee from another port (the one to the charcoal canister) and now the EGR works just fine. And it NOx emissions are reduced to about average, and the car passed smog inspection. Now I have to find out why the HC level is so high...passed that just by the skin of the teeth...