Thank you guys for your questions as they are right in line with the questions I had!

First, I too had been wondering how to verify the egr valve is opening when you can’t get your finger in there to see if the diaphragm is moving upward. I believe the brand of egr valve I bought for my 85 is a “Standard”. If the one I bought has the same hole as the AC Delco in the above pic, I will test it tomorrow by inserting one of the common red plastic spray tube thingies that they always include with spray cans like Gumout, WD-40, various contact cleaners, etc. This should work, correct?

Secondly, from the beginning of my thread I had it in my mind that the MightyVac book was right and my Fiero egr valve was wrong. Meaning this: the book clearly said you have to have at least 5 hg for the egr valve to open and mine was/is barely showing half of that. So, I assumed it was not opening.

Lastly, through all of my testing/detective work, taking apart, cleaning & testing the egr solenoid, I feel that I didn’t really find any smoking guns. (other than the low vacuum at the egr valve)

What is confirmed for sure is that it did fail smog twice for high Nox and I have not taken it back to the smog shop since A) because I don’t think I have done anything to resolve the issue and B) because of the mismatch of the MightyVac books insistence on 5 hg at egr valve when in reality I never got more than 2.5 hg.
Kit
P.S. you guys didn’t comment on the service manuals instruction on checking egr valve vacuum while in DRIVE.

[This message has been edited by Kitskaboodle (edited 10-15-2022).]

For reference, here is a pic from my MightyVac book showing the requirement of 5 hg at the egr valve….(look at the right page, top left area)
I also have to admit that I did not rev my engine to 3000 rpm like the book recommends to test egr valve vacuum but rather only 2000 or so. It seemed liked revving it any higher than 2000-2200 rpm didn’t change/raise the vacuum hg anyways.
Kit

[This message has been edited by Kitskaboodle (edited 10-15-2022).]

quote Originally posted by Kitskaboodle: P.S. you guys didn’t comment on the service manuals instruction on checking egr valve vacuum while in DRIVE.

I believe that's somewhat of a red herring, as how would it then ever be possible to check EGR valve vacuum on an engine in a car with a manual transmission (like my Formula)?

quote Originally posted by Kitskaboodle: It seemed liked revving it any higher than 2000-2200 rpm didn’t change/raise the vacuum hg anyways.

Yes... I was probably annoying my neighbors with some high revving in the driveway , and my readings never went above 2 inHg.

quote Originally posted by Kitskaboodle: First, I too had been wondering how to verify the egr valve is opening when you can’t get your finger in there to see if the diaphragm is moving upward. I believe the brand of egr valve I bought for my 85 is a “Standard”. If the one I bought has the same hole as the AC Delco in the above pic, I will test it tomorrow by inserting one of the common red plastic spray tube thingies that they always include with spray cans like Gumout, WD-40, various contact cleaners, etc. This should work, correct?

One thing I didn't think of trying at the time, was to connect the Mityvac directly to the EGR valve (with the engine not running) and applying more than 2 inHg vacuum (within reason, like maybe 5 inHg) to see if the EGR valve would actually open any further.

If you can get a probe inside the bottom of your EGR valve, maybe you can check to see whether additional vacuum (over what your engine normally seems to be applying to your EGR valve) makes any difference with the amount of diaphragm travel. If it doesn't, then you know for sure that there's no point worrying about your "low" vacuum reading.

[This message has been edited by Patrick (edited 10-15-2022).]

Ok, I have several things to report…..

I did some testing today on the new egr valve on my 85 GT and also on my old egr valve from my 86 GT. (which is off the car and on my workbench) Per Patrick’s request I checked both egr valves manually by applying some vacuum to them and observing if the diagphram is opening. When I applied a good 3 or more hg, the valve would open. Anything less than 3 hg, it didn’t seem like it was really opening. Both valves behaved the same way with the same hg. Also, I could tell they were opening because when you suddenly released the vacuum, there would be a plop or dink. (it was going back to it’s closed position) As a side note, when I applied 5 hg, they would hold that vacuum for a while, only sinking down maybe to 4 hg.

Ok, after these tests I then went back and re-checked the vacuum again while teed in to the egr while the engine was warm. I revved it to 2200-2400+ rpm and for some reason I was now getting 4-5 hg on the vacuum gauge. So, I decided to go and do another re-test at the smog shop (since I was NOW) getting better vacuum TO the egr valve. Well, it failed again for the third time. ☹️
Here is a pic of the emissions test numbers. I noticed that it seems to be failing the 15 mph test but passing the 25 mph test.
Your thoughts?
Kit

[This message has been edited by Kitskaboodle (edited 10-15-2022).]

[This message has been edited by Notorio (edited 10-17-2022).]