Well, the XJ failed smog for the second time. First time failed at the tailpipe, fixed what needed to be done and now it failed "EGR Function". The tech said that he was able to manually operate the EGR with vacuum, however, he could not get it to function on its own. I know there is a EGR solenoid located by the air box and that is what he suggested I look at. How can I test this to ensure it is functioning properly? I don't have a service manual and have been confused with my online searches thus far... I'm not very familiar with the whole EGR mess. Thanks in advance!

I didn't know they had an EGR valve back then. Neat.

To test the solenoid, you can apply 12v and ground to the terminals. If the solenoid works, the engine should stumble at idle, maybe even die if the EGR valve opens.

Here are 2 links to test your egr.

http://cruiser54.com/?p=119

http://www.lunghd.com/Tech_Articles/...iagnostics.htm

Make sure the vacuum lines are intact.

Note from DJ

With what did the inspector apply vacuum to the EGR valve?
Was the engine running when he applied the vacuum?

If the Jeep is not meeting these requirements the ECU will not create a ground for the EGR valve to operate.
The engine needs to be running and at normal operating temperatures with engine speed above idle, then the solenoid valve is de-energized, allowing vacuum to the EGR valve. Now that the EGR valve is de energized it will allow some exhaust gases to be interred into the intake manifold.

Under conditions of engine warm-up [water temperature is below 115 degrees F or 46 degrees C] the engine is at idle, wide-open throttle, or rapid acceleration or deceleration, the solenoid valve is energized and blocking vacuum to the EGR valve.

Note from DJ
The reason for all the questions is I have 88 Cherokee that has been Smogged in the Los Angeles area for the last 24 years. The last inspection was 7/10/2021 and they have never checked my EGR system in all of the years.

I'm very sure they did. All it takes is a few blips of the throttle and you can see the EGR valve move when it's working properly.

Odd I don't see NOx values but he passed the emissions portion.

Thanks for the help guys! So I'm able to move the EGR diaphram manually and get the engine to die out. The solenoid seems to be working fine after running those recommended tests. I get vacuum to the EGR when I blip the throttle. I can tell that the diaphragm is moving because I can see the plunger deal move. It doesn't move a whole lot, is it suppose to move significantly? I found my old manual and ran those tests. I don't have a vacuum gauge, but I can tell it has vacuum.. should I go grab one and get some actual numbers? I think I'm going to call the tech today and try to figure out why he failed it.

Note from DJ

Yes if it was me I’d want to know why it failed!
Post back when you find out so we learn something.

It only moves a little bit. Sounds like it's working. Does it still have the transducer attached (black saucer shape)?