YJ and EGR questions

We have a 89 YJ with an 85 4.2L that has all the 85 and some 89 stuff on it. Currently it has an EGR valve but the pulse air is not installed, we have the cat and it is going back in next paycheck when we get the exhaust system done. My son now works full time so he's paying for it now but it's going to be a little bit at a time. He just did all tha vac hoses last nite in the auto parts parking lot [one of those 'take one off, run in, get a new one, run out, put it on]. The ECU is 89, carb is 89, intake and exhaust is 89. At any rate while he was working on it a biker with a custom built HD pulled in and helped him, told him the EGR is bad. To my way of thinking if the cat is off, no pulse air then the EGR should have no effect on the running of the engine. Now the vac line is still connected but in this type of setup can the EGR have an effect ???
Never had an engine with an EGR before so I don't really know what it does and I don't want him to waste $56 on a new one until we do the rest of the plumbing.
I've also been looking at what called the 'nutter bypass' but have mixed feelings on it.

Its been a while since i messed with a carbed motor but the best way to tell if the egr is bad is to remove it and for 1 see if the diaphram and plunger are moving the up and down and secon after you push it in hold your finger over the vacum nipple to se if the diaphram leaks if it does the plunger will come back out if not i would say its good. other things can make the erg to actup like carbon build up in the port and intake area for the egr. brake clean and a screw drive works good. hope this help. some may disagrea with someof this as far as my testing method but its eaiser than doing the hole vacume test BS.

The EGR recycles a portion of the exhaust to the intake to control combustion temps and reduce NOx.

On my '84 XJ Wagoneer, the EGR circuit also has a solenoid in it. Don't know what it does, I had enough trouble trying to figure out the vacuum lines because I didn't have the luxery of removing one and replacing it before proceeding to the next. I had to reconstruct from a blank slate.

Essentially, if you don't have emissions testing in your county you don't have to worry about the EGR. If bad it may cause rough idle, but it won't kill anything. If you do have emissions testing, it's time for you and your son's EGR to become better acquainted.

No, no testing but someone said that it just can't be removed and blocked off with a plate either, burned valves would result or so they said. The diaphram seems to be ruptured or damaged from what one of the KNOWLEDGABLE people at the parts store we deal with.
Well, monday will tell the tail when we stick a new one on.

with the moter running you hook vacum line with suction on it to the egr it should make the engine run bad,if not egr is probly defective,or with egr still installed,w engine running push up on under side of diapham it should run poorly.

Generally, you can't just pull out an EGR valve, because the way its plunger and passages are arranged, it will end up passing exhaust gas all the time, rather than none of the time. If the valve is not currently leaking (assume this if the engine idles well) the best way to disarm it is simply to crimp off its vacuum line.

EGR, when it works, tends to reduce engine knock, especially at cruising speed. If you have an XJ you'll never know it, because the knock sensor will compensate.