emission control causing rough idle?

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Check for vacuum at the hose to the EGR when the engine is idling. There should be none. If there is vacuum, you will need to make sure that all of the vacuum hoses are connected properly and that the EGR is not connected directly to manifold vacuum.
You will need a FSM or at least a Chilton's or equivalent manual to verufy proper hose routing. Just going out and spending $25 on a new could prove to be a waste of money
if you don't know for sure that the valve is bad.
 
I have a Haynes manual, shows the routing of all hoses. Will double check these a well.. Thanks
 
I;ve been trying really hard to nip this problem, maybe I'll wind up at the Dealer and their tech will get on here too!! Cause I bet none of em know anything bout these old engines.....
 
Flickering lights are an indication the charging system needs attention; we'll get to that, what's your line voltage at hot/slow idle with the car in Drive?

Pull EGR stem to kill engine means EGR valve is probably sealing properly. It could be causing a rough idle if there is a small leak through it, but I don't think you'll see improved idle quality by blocking it off, but it's easy to try, so go ahead and try it if you like. Buy a new EGR valve gasket, remove the valve, clean the mounting surfaces, install the new gasket, and install the valve upside-down from its original position; this will block off the EGR just as surely as any blockoff plate you might buy or make.

There will be no "air/fuel mixture imbalance" (?!) of any type as a result of disabling the EGR, and you will not need to do any rejetting. However, you may encounter spark knock on acceleration, because the distributor advance curves were set up to take EGR into account.

Have you checked for timing chain slop? Remove the distributor cap and turn the engine by hand (w/fan and belt) until the rotor starts to turn. Keep one eye on the crank pulley and the other on the rotor as you then turn the engine the other direction and see how far you can turn it before the rotor starts turning.
 
Sounds like the EGR valve passages are not clogged but you could still have a leaky valve. Check the manifold vacuum at idle if you have a gauge. If not, dribble a little gas from a primer can into the top of the carb and see if the idle smooths out. If so, you have a vacuum leak somewhere. You can spray Berrymans, WD40, or similar around all the carb and intake gasket surfaces to check for a leak also. I have to disagree with slantsixdan on the mixture part....when the EGR valve is open there is a dilution of the air charge in the intake which will also effect the mixture. My testing has found that an engine designed to run an EGR valve will tend to ping and run richer if the EGR is not working.
 
Yes and when he gets a flash fire from dumping something flammable into a running engine following your advice, won't you just feel good? I never advise anything flammable looking for vacuum leaks. I cannot for the life of me figure out why in the world people do it and they do it all the time. Water in a spary bottle works just as well, if not better with no danger of fire. I have seen a person go to the ER for 2nd degree face burns from an under hood fire and explosion because he was using carburetor cleaner looking for vacuum leaks. I strongly advise against it.
 
StrokerScamp said:
Yes and when he gets a flash fire from dumping something flammable into a running engine following your advice, won't you just feel good? I never advise anything flammable looking for vacuum leaks. I cannot for the life of me figure out why in the world people do it and they do it all the time. Water in a spary bottle works just as well, if not better with no danger of fire. I have seen a person go to the ER for 2nd degree face burns from an under hood fire and explosion because he was using carburetor cleaner looking for vacuum leaks. I strongly advise against it.
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You're right.....I wouldn't recommend "dumping" gasoline under the hood of any vehicle for any reason. As long as the engine isn't backfiring and it's just at idle adding a few drops of gas from a primer can won't cause much of a fire if something did go wrong. I have never had a problem with using Berryman's or WD40 for checking gasket leaks in the 40+ years I've been doing it so didn't realize others have had a problem. You've actually had a car catch fire using those products?
 
Matter of fact, the incident I referred to happened in the auto shop I took auto mechanics in when I was in high school. The guy was using carburetor cleaner, and we figured it hit a plug wire that was bad.....but nuthing was left under the hood so we couldn't tell. BUT, it lit the spray out of the can and went all the way TO the can and it exploded in the boy's hand. Carburetor cleaner is more combustible than gasoline under the right (or wrong) circumstances.....and I guess those were them. I still see him every now and then because he lives local. You can still tell somethin happened and that was in the real earlies 80s. It was unfortunate to say the least. WD40 is even more combustible than gasoline.
 
cudamark said:
My testing has found that an engine designed to run an EGR valve will tend to ping and run richer if the EGR is not working.
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Interesting test...since rich mixtures reduce the tendency to ping. Think about this logically for a moment: the idea was to clean up the exhaust. Cleaning up NOx emissions meant reducing peak combustion chamber temperature. This was done with EGR, which dilutes the air/fuel mixture -- not just the air supply, not just the fuel supply -- headed into the cylinders. If you find that logic kind of hard to follow, then go look up the jetting details of carbs used with vs. without EGR. They are in almost every case the same. There is no rejet required and the engine will not run rich by disabling the EGR.
 
If you decide to install a new EGR valve, you can update to a more advanced type that is a direct bolt-on. Standard #EGV490; RockAuto's got them on sale for under twenty bucks and you can knock that down further with those 5% RockAuto discount codes that are always floating around. This valve has a backpressure transducer that modulates vacuum to the EGR valve to match EGR flow rate better to the engine load. Takes a smaller bite out of driveability than the non-transducer type valve.
 
slantsixdan said:
Interesting test...since rich mixtures reduce the tendency to ping. Think about this logically for a moment: the idea was to clean up the exhaust. Cleaning up NOx emissions meant reducing peak combustion chamber temperature. This was done with EGR, which dilutes the air/fuel mixture -- not just the air supply, not just the fuel supply -- headed into the cylinders. If you find that logic kind of hard to follow, then go look up the jetting details of carbs used with vs. without EGR. They are in almost every case the same. There is no rejet required and the engine will not run rich by disabling the EGR.
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My understanging is that the H2O in the exhaust is what helps quench the combustion temps...that is why water injection is so effective in reducing pinging problems. The carb jets are the same in most cases. The EGR doesn't change the air/fuel ratio in the carb....it slightly leans it after the carb only when the valve is open. The only evidence I have for this is the readings I've seen on the smog machine. When the EGR was not working, the HC's read higher than when it was. Not a lot, mind you, but it was measureable. I don't run a smog testing station but a friend of mine does and the tests were done in his shop on vehicles I've had in for testing. A limited sample I'm sure and there may be other engine combos that work differently but I would think the principles would be the same for most vehicles. Any smog guys out there that can refute or verify this info?
 
slantsixdan said:
If you decide to install a new EGR valve, you can update to a more advanced type that is a direct bolt-on. Standard #EGV490; RockAuto's got them on sale for under twenty bucks and you can knock that down further with those 5% RockAuto discount codes that are always floating around. This valve has a backpressure transducer that modulates vacuum to the EGR valve to match EGR flow rate better to the engine load. Takes a smaller bite out of driveability than the non-transducer type valve.
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I WENT OUT AND FLIPPED THE VALVE, NO CHANGE NOTED. When it stops freezing here,..yes freeze and snow in Houston believe it or not, I plan to check for slop in the timing chain. No vacuum leaks detected, but manifold fitting really sucks in the air when uncapped. I'm starting to lean toward a timing problem, or an alternator output problem. How far should the pulley travel around before the rotor turns?

Thanks Dan,

Gary
 
cudamark said:
My understanging is that the H2O in the exhaust is what helps quench the combustion temps
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No. EGR reduces peak combustion chamber temperatures because exhaust is not combustible, so diluting the (combustible) air/fuel mixture with (non-combustible) inert exhaust gas means the fire in the cylinder is not as hot. Go read up on EGR (better, more detailed description in the Stockel and Peterson books described in this thread.)


The EGR doesn't change the air/fuel ratio in the carb....it slightly leans it after the carb
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No. The EGR does not affect how rich or lean the mixture reaching the cylinders is. It affects how dense, in a word, the combustible air/fuel mixture is.

When the EGR was not working, the HC's read higher than when it was.
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Right. That's not because the mixture goes rich with non-working EGR, it's because there remains some unburned HC in the exhaust, and a portion of that is sent back through the engine (via EGR) and thus burned the second time around, leaving less unburnt HC at the tailpipe.
 
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