emission control causing rough idle?

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Remove the valve, make a block off plate the shape of the port on the intake where the valve came off, bolt it on with either some high temp silicone or a gasket and plug off the vacuum line.
 
I think this can be achieved by cutting a piece of flashing the outline of the valve base, and bolt it back using high temp silicone , the valve will still be there, but blinded between valve and intake. What do you think of this idea?(slip flashing between)
 
Yep, sorta like putting a roof vent on your house without ever cutting the wood.
 
That has to be the problem, i've done everything, valve adjustment, new dist. new carb, wires plugs cap rotor... name it , running out of options for process of elimination...
 
I don't understand why you would not want to simply remove the valve......or better yet, diagnose to verify that the valve is bad and if so replace it. To me, that would be the best option, but that's not what you originally asked. I simply answered your original question. Especially if there are inspections where you live, you might want to consider a proper diagnosis to verify the valve is bad and then replace it. I'm sure if the valve being bad is the cause of your problem the installation of a new one will straighten it right out and then it will be operating as designed and probably still pass inspection.
 
It is too old for a required emmision test in Texas, its a Cal. car, and I just want to simplify things. The emission system on this thing is an easy way to develop vacuum leaks, I say do away with it if not mandatory.
 
Just block the sucker off and call it a day . When EGR is functioning properly , it's a good thing ; but when it starts giving ya fits ya gotta either service it ( it may be plugged with carbon , as will any heat crossover ... not sure if the Slant Six has such a thing ... ) , replace it , or dump it .

If you service it -- and the breather / rest of the PCV system -- and the problem persists , then block it off .
 
Fair enough. However, you would still be best served by a proper diagnosis. Without that, you are merely guessing that the EGR valve is bad. It is fairly easy to diagnose. Simply verify you have vacuum to the valve at part throttle with a vacuum gauge. Once verified, pull a vacuum on the EGR valve and see if it opens. If it fails to open, then the dashpot is ruptured. If it seems to open, you can diagnose further by removing and inspecting the valve to make sure it is closed completely. Carbon buildup caked around the orifice will cause a manifold vacuum leak and the rough idle condition. You might can get by with cleaning it and putting it back on and all is well. You never know. Either way, at least if you diagnose it, not only will you learn something, but you will find the problem.
 
I've been doing a lot of research on this, these early (1974) emission control systems are a mess!!! In fact, in 1975, they installed a light in the dash so that you would service, clean, or replace the E G R valve every 15 K miles.... gonna do away with it...
 
StrokerScamp said:
you would still be best served by a proper diagnosis. Without that, you are merely guessing that the EGR valve is bad.
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Yeah, what ↑he said↑. Guessing at a problem usually doesn't give a satisfactory, complete, or cost-effective fix. There are many, many causes for rough idle beyond the obvious ones. A leaking EGR valve could cause a rough idle, but so could many other things. How many miles are on this engine? How exactly did you do your valve adjustment? Tell us about the procedure you used. Cam timing could be off due to timing chain stretch. Ignition timing could be off due to vibration damper outer ring slip. Could be vacuum leaks at the manifold-to-head junction. Could be exhaust leaking through a crack in the intake floor (blocking the EGR valve won't help this). Could be vacuum leaks elsewhere in the engine bay. Could be a carb problem not addressed by the rebuild. Could be weak ignition caused by a weak spark box or low primary voltage caused by high resistance in the wiring harness or by weak alternator output at idle.
 
Dan, I;ve been waiting on your input on this, I followed the method for valve lash adj. described by you, engine running,I have no vacuum leaks,I tested with carb cleaner,one thing you said sparked me... at night when the engine is idling, the lights flicker a bit, may be fire from alt...dont know how to check the other possible probs, you guys' input is always welcomed. Thanks Gary
 
I would start by disconnection the vacuum hose to the valve and see if that helps the idle. If so, you may have vacuum hoses hooked up wrong or a bad vacuum amplifier. You can also operate the EGR valve by hand to see if it makes the idle worse when it's open (it should). Just reach around the back side of the valve and pull the rod away from the intake. You may want to do it with some needle nose pliers or a screw driver if the engine is hot so you don't burn your fingers. I've seen those valves get bent and not close all the way so give it a good look to see if it's straight. I would repair the system rather than just block off the valve. You could have other driveability problems as a result. They were designed to have that valve working and if it doesn't, you could have an air/fuel mixture imbalance. Now if you want to rejet or change the carb for a non-EGR engine.....knock yourself out.
 
gpreston57 said:
Went out, started it, let it warm a min. , pulled up on the stem, engine died.... what now?
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It sounds like you get to start your diagnostic procedure all over again; I believe that the only way the EGR valve could cause a rough idle, is if it were open at idle, which it's not supposed to be. When you pulled on the stem you opened the valve. Remove the valve and clean it to verify that there is no carbon holding it part way open. Verify that there is no vacuum at the valve at idle. If it's not stuck part way open and there's no vacuum, you can eliminate that as the cause. As Dan said, a crack between the intake and exhaust could cause your problem, essentially acting as a permanently open EGR. What is your vacuum reading at idle?
Idling problems on these 70's engines can be very difficult to diagnose, especially since the emissions controls complicate the issue even when they're not the cause.
 
the EGR will cause idle problems when it doesn't close completely, often do to being dirty, the further it is open at idle the worse it will run, that is why it died when you opened it all the way
 
Yup, you created an instant manifold vacuum leak and killed the engine.
 
the EGR or exhaust gas recirculation valve is designed to only open under load in order to allow a small amount of exhaust into the combustion chamber in order to lessen the formation of nitrogen oxide NOx, when they get dirty soot can build up on the valve preventing it from closing completely and causing a rough idle,
if it's not to bad you may be able to take it off and clean it
 
EGR only works at part throttle as manifold vacuum under load is either slim or non existant.
 
That valve is only 25 dollars at autozone, I was just thinking of ways to eliminate unnecessary things, haven't checked vacuum at idle, cause it too cold out there this week. When it warms up a bit, I'll check it, and put a timing light on it again...if thats good, I guess I'll get a new EGR valve.The engine runs down the road good, lots of power, the only thing that bothers me is at idle, under a load, the wheel and dash vibrates, drives me nuts....
 
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