Sounds like its too late, but for the archives, here's how to quickly and easily test your EGR valve and modulator.

1) Start engine and let idle for a few minutes.

2) Disconnect hose from EGR modulator to EGR valve. Rev up the engine (via an assistant or just moving the throttle lever). Make sure the hose from modulator to EGR valve has increasing vaccuum as RPMs increase. If yes, modulator is fine. If not, modulator is bad.

3) Hook the hose from step #2 up to the EGR valve. Apply vacuum to the hose (I did this by mouth, but a pump would be better). If the engine starts to sputter and die, EGR valve is fine (the EGR valve is opening when vacuum is applied as it should. Normally this happens at higher RPMS with advanced timing so the engine does not sputter. However, at idle, it will make the engine sputter). If the engine does not start to sputter and die, your EGR valve is probably stuck shut.

*Note: if you wanted to be real precise, you could test what the vacuum pressure is from the modulator as the RPMs increase and then see how much pressure is required to open the EGR valve. I think the valve opens around 2500-3000 RPM, so the modulator vaccum pressure at 2500 rpm should roughly match the pressure required to open the EGR valve.

Side note: I think my EGR valve is opening too early (rather than too late). I used some hardware (basically a bolt, a nut, and a few washers) so I can adjust the constriction of the vac hose from the EGR modulator to EGR valve. I'm still playing with this seeing how much constriction I can get away with before throwing a trouble code and how much of a gas mileage improvement I get. I'll post the results in a few months when I know for sure if it helps at all.

Good luck w/ your problem. Hopefully the new modulator will fix it.

Good sign that your EGR is opening too early is a rough inconsistant idle. After installing the Street RV head I had such strong manifold vaccum that my original EGR was being pulled open at 850 RPMs. I messed with damn near every sensor and adjustment under the hood trying to figure out the idle problem. Then out of the blue after applying vaccum to the EGR valve directly and it passing...it hit me. Ya know...my idle seems like a mild case of what happens when testing these things. Pulled my EGR and sure enough, the thing wasnt closing all the way thus allowing exhaust gases to intermixate ( <img src="/forums/images/graemlins/notooth.gif" alt="" /> ) at idle when the ECU wasnt compensating for it. Just a thought you may want to check. After replacing EGR with a spare things was fine. Of course the I have Zero vaccum going to the new EGR now...and it opens up on its own as RPMS increase...NO I aint kidding!
~Darin <img src="/forums/images/graemlins/baby.gif" alt="" />

Hey guys, All is NOT well....
I replaced the faulty vacuum modulator with a new one, and the truck ran great after resetting the ECU. (Doesn't it always?)
WELL- I ran it about 50-60 miles (To work and 1/5 of the way home) and it ran GREAT...5th gear up hills, power to pass, etc. It felt like a new truck again UNTIL I was heading home...
Heading home the #@$#@%$#%#^%%#@@!EDSF#@#@$#ing check engine light came on again. I was in awe. (not really, but it sounds dramatic)
Okay, so the EGR valve is most likely the culprit now, and that brings me to my next question:
DOES ANYONE HAVE A SPARE 3VZE EGR VALVE that the would sell me? PLEASE?
I cannot afford to keep sticking hundreds of dollars in this thing, and I would just like it to get back to how it ran before. THANKS!

yea those EGRs are expensive.. . are you sure thats the problem?? did you replace that little black round thing i was talkin aobut.. maybe thats the same thing you said you replaced shoulda been cheap like 30 bux or less i beleive. i don't thinki ts your EGR .. you can always take it off and clean it.. i ddin't do it to mine .. i stupidly blew compressed air threw it DO NOT DO THIS, it didn't hurt mine i don't think but its not good. to clean it i think you're supposed to soak it in brake fluid.. there are lots of posts on here about it. have you checked your egr by pushing the plunger up threw one of the holes?? it should stall the motor. if that happens than the egr is functioning correctly . <img src="/forums/images/graemlins/ignore.gif" alt="" />. i think?? someone chime in if i'm wrong.

i was told the black thing is the EGR recirculator.. it made my NOx high on the emmisions test. hope this helps.. sorry i know how annoying that check engine light is.. i've been driving with it on for umm 4 months.. so i just put a picture over it <img src="/forums/images/graemlins/notooth.gif" alt="" />

<img src="/forums/images/graemlins/cheers.gif" alt="" /> <img src="/forums/images/graemlins/kewl.gif" alt="" /> goodluck

Don't buy a new one until you have CONFIRMED the problem. TEST IT as described and if it flunks, then buy one. The only guys on here that are going to have spares are the ones who bought a new one only to find out nothing changed.

As I posted before, just disconnect the hose that goes from the modulator to the EGR valve. Apply some vaccuum and see if it makes your engine sputter while idling. If so, your EGR is probably fine. If not, you might want to clean the EGR valve. Also, you can push the EGR valve up from the bottom through the 1/4" or so holes. BUT, you could ruin your EGR diaphram doing this and then you really will have to buy a new one, so I would just try applying vacuum.

Finally, you probably already know this, but the modulator is the small, round plastic thing with two hoses going in and one going out (to the EGR valve). The EGR valve is the round metal thing with a metal tube going to the exhaust manifold, another metal tube going to the intake, and vac hose going to the top of the round metal thing.

Bringing an *old* thread back up...

I tested mine yesterday, after getting a CEL that went off after one key cycle and hasn't returned. I could discern no increase in vacuum from the modulator (testing the bottom connector), and couldn't even apply vacuum to the valve through the tube to the modulator. The tube is in good shape, so what does that tell me?

Mark