Scenario: Not passing smog (high NoX.) Replaced EGR valve (from Autozone) and still doesn't pass. Diagnostics done at the dealer said that my EGR is not opening up. I checked for vacuum going to the EGR valve and there's a strong vacuum around 2000 rpms (the test instructions that came with the EGR valve from autozone said to do this to check if the vacuum solenoid to the EGR valve is functioning properly.) I can't physically push or press on the diaphram to open the valve, so I'm guessing it's not a stuck valve (since it's new.) What else could I check to determine why the EGR valve is not opening?

The EGR passages tend to get clogged-up after a while. Try connecting a vacuum pump (or some other source of vacuum) to the EGR valve. Apply a vacuum to the valve with eng idling. The eng should die or almost die when valve opens. If there's no difference in the way eng idles, the passages are clogged and will require removing the intake manifold to clean them out.

If the EGR valve is good, and the solenoid works, assuming the ECM is commanding the solenoid, to apply vacuum and it does then ther EGR ports are clogged (as ZZ28ZZ said,) this can also affect the EGR thermal switch which in turn affects how the ECM commands the EGR solenoid. ChevyThunder has some good diagnostics for the EGR and also a fix for the EGR Thermal switch - believe me this little sensor is expensive (Wells part no. EDS4 ~$74.00+tax)
There's a wealth of valuable information on this site.
The EGR is not the main subject so just scroll down until you see the EGR diagram (hand drawn.)
Chevy Thunder.com -Knocking, or Pinging

i know..... @ oreilly's it $12 and borgwarner at that.

The motor is a brand new crate motor and I cleaned out the intake manifold when I put it in.

I tried using a vacuum pump to open the EGR valve and I couldn't create a vacuum. I remember reading instructions that came with the EGR valve that said that the valve is used in a positive back pressure system and a vacuum pump will not work on this kind of system. Why would a vacuum pump not work on this kind of system?

Is is possible to shove a flexible tool down the EGR ports to see is there are any obstructions? Basically I want to make sure there are no obstructions without pulling off the intake. I'm pretty sure that the ports are clean, just a sanity check.

Thanks for all your help! I'm gonna keep troubleshooting. If you have any other ideas, please post them. Thanks!

Please provide engine specification, make & model of car.

here's a page on testing both negative & positive back pressure EGR valves.
Tech Tips

http://sdpc2000.com/cart.asp?action=...id=128&pid=105

It's a 350 5.7L roller block used in 92-93 Caprice or Fleetwoods.

It's in an '87 Camaro Z28, originally a 305.

Thanks for the link to troubleshooting all types of EGR valves. If I'm not mistaken, the one for my year car is the positive backpressure version. Could some one verify this?

Do you have a part no.?

Update:
On the Autozone Online Store a search finds:
UpDate:
The above valve can only be tested at high rpm, or off vehicle as stated on "Tech Tips"
The type of EGR valve is tranparent to the ECM, so using a negative back-pressure type should solve your problem unless the solenoid, and or the ECM is defective.

Have you tested the EGR vacuum solenoid?

I'll get back to you on the part number, but I remember reading that quote you put in there, that's why I was wondering how else can I test the EGR valve. I'll try testing it using "Tech Tips."

The way I tested the EGR vacuum solenoid was to put the car in drive and have a friend "feel" for vacuum on the end of the hose where the EGR valve would normally go. I brought the rpms to about 2000 and my friend "felt" vacuum. I didn't have a vacuum pump/gauge at the time, so I couldn't verify how much vacuum I had.

I'll get back to the post when I find the part number.

The part number written on the top of the EGR valve is 17087263

The 17090149 EGR is a negative back-pressure valve

I traced your EGR valve to a company in Germany "KTS American Parts."
On their online catalog I did a search for "EGR-Ventil" using the 92 caprice 350 5.7L, and I got O.E.M. numbers 17090149, and 17112334. These cross-reference to a WELLS EGR158.
This valve is a negative back-pressure type. You should be able to test it "off engine" with a Vacuum pump

I grabbed jpg images of the sites, I can email them to you if you want them.

I was looking at pictures for the Caprice EGR valve and the screw holes do not match up with my intake manifold.
I wonder if there is a difference between the 305 ci engine EGR valve versus the 350? Anybody know?

Is there a difference between an EGR for a 305ci engine and a 350ci engine besides the part number? I did a 305 to 350 swap, and the EGR system is the only thing that is not working properly.

I'm still troubleshooting the entire EGR system, and I can't find what's causing the EGR not to open up except for the fact that I'm using a 305 EGR on a 350. Thanks in advance.

Updated link to Tech Tip article RGarcia pointed to above.

http://www.champion-auto.com/Documents/52_EGR.pdf

hey I have a question for you I have a egr valve for a 87 5.7 iroc tpi and I don't have the orignal part # to find out which restrictor washer to use that came with the new egr valve do you have any idea where I can find this part #? Thanks