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1974 Cadillac 472 eng EGR valve problems

Started by Scot Minesinger, August 21, 2014, 05:16:00 PM

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Scot Minesinger

Working on a 1974 Cadillac and it looses power consistent with EGR valve failure.  I want to replace it but, they are not available.  Interested in the car running good, not benefits it may provide for emissions.  If I plug the vacuum line and let the spring work, will that make it run well again?     
Fairfax Station, VA  22039 (Washington DC Sub)
1970 Cadillac DeVille Convertible
1970 Cadillac Sedan DeVille
1970 four door Convertible w/Cadillac Warranty

TJ Hopland

Power loss consistent with egr failure?  Can you describe this further?
StPaul/Mpls, MN USA

73 Eldo convert w/FiTech EFI
80 Eldo Diesel
90 CDV
And other assorted stuff I keep buying for some reason

Scot Minesinger

Car starts and runs fine for the first fifteen minutes.  Then under load it looses power after thoroughly warmed up.  This happened exactly before and the EGR valve replacement was available, and cured the issue.  Now it does not seem to be available.  Funny how this same symptom occurred in my 85 Caprice, 95 Fleetwood and 96 Suburban, all cured by EGR valve replacement.

Could I just make a 1/8" plate and place it between block and valve with gasket so it would simulate constant closed situation to make it run better?  What does this do bleed exhaust back into intake for re-burning?  Maybe it gets dirty and get's stuck open?  If this is the case, blocking it off seems the way to go.
Fairfax Station, VA  22039 (Washington DC Sub)
1970 Cadillac DeVille Convertible
1970 Cadillac Sedan DeVille
1970 four door Convertible w/Cadillac Warranty

RussK

If you unplug the vacuum line off of the EGR valve it should stay closed, if it doesn't close all the way it will cause a bad idle, or stall it out all together.
you can make a block-off plate if you need to get rid of it all together, or just leave it closed, both ways its the same.
the EGR was mostly to cool down the cylinders for more NOX control, and it will run fine without it.
Russell kidd

"Cadillac Kid" Greg Surfas 15364

Scott,
If the problem does not occur until the motor is warmed up (and if it is in fact due to the malfunctioning of the EGR) then apparently both the thermal delay and the EGR actuator seem to be functioning.  You might just pull the valve and clean it.  It's amazing how much crud can develop in only 40 years.
Greg Surfas
Cadillac Kid-Greg Surfas
Director Modified Chapter CLC
CLC #15364
66 Coupe deVille (now gone to the UK)
72 Eldo Cpe  (now cruising the sands in Quatar)
73 Coupe deVille
75 Coupe deElegance
76 Coupe deVille
79 Coupe de ville with "Paris" (pick up) option and 472 motor
514 inch motor now in '73-

Scot Minesinger

Greg,

Hoping you would answer this.  I will be removing the valve.  Would really like to make this bullet proof.  Will the car run fine if I just blank of the valve with a piece of 1/8" metal cut same as gasket except only mounting holes drilled in it, and then reattach valve with plate and new gasket, essentially removing the function of the EGR valve so it can never open?

If not will clean it.
Fairfax Station, VA  22039 (Washington DC Sub)
1970 Cadillac DeVille Convertible
1970 Cadillac Sedan DeVille
1970 four door Convertible w/Cadillac Warranty

R Schroeder

#6
I removed mine 3 years ago. Made a 1/4 plate to cover the hole, and used the gasket from the EGR valve. Car runs and idles perfect. Plugged off the vacuum line.
Roy

I also plugged the vacuum line to my heat riser off. It is in the open position all the time. Car is not used in winter, so there was no need for it.
Eliminates the chance of it getting stuck in the closed position.

Jon S

Quote from: RussK on August 21, 2014, 08:13:23 PM
If you unplug the vacuum line off of the EGR valve it should stay closed, if it doesn't close all the way it will cause a bad idle, or stall it out all together.

Exactly.  If it idles smoothly with vacuum line disconnected and plugged but still loses power under load, it is not the EGR causing the problem.  A simple way to eliminate or validate a culprit. 

Jon

1958 Cadillac Sedan De Ville
1973 Lincoln Continental Coupe
1981 Corvette
2004 Mustang GT

"Cadillac Kid" Greg Surfas 15364

Scott,
There are a few "warm-up" devices originally incorporated in the emission systems of this car.  Check them all for compliance with original design, or verify they have been correctly "bypassed".  The EFE "system" sensor, vacuum lines and actuator, being one.
Greg Surfas
Cadillac Kid-Greg Surfas
Director Modified Chapter CLC
CLC #15364
66 Coupe deVille (now gone to the UK)
72 Eldo Cpe  (now cruising the sands in Quatar)
73 Coupe deVille
75 Coupe deElegance
76 Coupe deVille
79 Coupe de ville with "Paris" (pick up) option and 472 motor
514 inch motor now in '73-

TJ Hopland

I'm with John and Russ thinking this does not seem like an egr issue.   Your other cars have computers, especially the 90's ones so on those the computer controls the egr operation along with other aspects so I could see even on the 85 that an EGR issue could cause what you describe.  Its not likely the EGR on its own that caused the issue.  Its that the computer told the egr to operate and was expecting a result so it made a change in timing or fuel to go along with it and what you felt was the result of the cut in fuel or timing without the EGR flow.  The 90's stuff actually could have had position sensors on the valve and additional pressure sensors to monitor the function and flow.  The 80's it just looks for the change in manifold pressure and assumes its working.   The non computer stuff its all just the delicate balance that works most of the time.   EGR opens based on throttle position and manifold vacuum.  The result of the opening changes the vacuum which may be enough to change the valve position.  The change in vacuum changes the amount of fuel being drawn in and would also change the timing through the vacuum advance.   This all works fine in steady states.  Its the transition states where it gets interesting and where a fast computer and EFI really shines.

Are valves really not available?   Seems like just recently someone got one for a similar car.   It was a universal fit one where you had to install a specific orifice washer depending on the model you were replacing. 

A Chevy fuel pump block off plate is a good start for an egr plate.  IIRC the holes just need to be elongated a bit.  Those are available in the 'hot rod' section of most parts stores.

The EGR valve has the seat portion of the valve sticking down into the intake so you can't really just put a sold gasket on to block it.  That seat is supposed to come off but most of the time they are pretty well sized in place. 

IF you are trying to cover it you want to also disable the EFE (exhaust flapper valve) if the car has one.   If its still there and working it will tend to burn up most gasket materials on your block off plate.  With the EFE open there won't really be any flow up there so things run cooler including the gasket.   When the EFE is closed it basically forces all the exhaust from the one side through the intake to the other side.  Another down side to messing with all this is the choke heater is also in the intake so it may take longer for the choke to get open.  You will want to monitor it closely at first to make sure the choke does get open and stay that way after things are warmed up.   Unlike many other intakes of the era the Cad one does not have any coolant in it.   

Some engines removing the EGR makes em cruise very lean.  Thats good for MPG but bad for heat and you can end up burning pistons.   Had a friends car that he ended up pulling out so much timing to try and keep it form detonating at cruise that it totally killed the performance.  We ended up putting the egr back in and that let us put the timing back and everything was happy again. 
StPaul/Mpls, MN USA

73 Eldo convert w/FiTech EFI
80 Eldo Diesel
90 CDV
And other assorted stuff I keep buying for some reason

Scot Minesinger

Thanks guys, the snorkel mounted damper actuator is set up so it stays in the open to fresh air/closed to drawing air across exhaust manifold position.  Likely the EGR is dirty, and I will probably blank that off, as Roy has said the car will still run fine.
Fairfax Station, VA  22039 (Washington DC Sub)
1970 Cadillac DeVille Convertible
1970 Cadillac Sedan DeVille
1970 four door Convertible w/Cadillac Warranty

waterzap

#11
Any EGR that will fit will work. You can manually change the opening with washers. When the engine is in idle, the EGR should be closed. Once you start driving, it should open up. Thats about it. You can probably make it so the EGR is only open at higher cruise RPM's. Rock Auto has a closeout on the 75 EGR for $5. There are only a few left, so getting one is probably a good idea to try out.
Leesburg, AL

"Cadillac Kid" Greg Surfas 15364

Scott,
The EFE system controls what used to be called the heat riser; the actuated damper on the right side exhaust manifold that directs exhaust gasses through the passage of the intake manifold.
Greg Surfas
Cadillac Kid-Greg Surfas
Director Modified Chapter CLC
CLC #15364
66 Coupe deVille (now gone to the UK)
72 Eldo Cpe  (now cruising the sands in Quatar)
73 Coupe deVille
75 Coupe deElegance
76 Coupe deVille
79 Coupe de ville with "Paris" (pick up) option and 472 motor
514 inch motor now in '73-

waterzap

Just want to add. Pulling the vacuum on the heat riser might be a very good idea. I would rather have it open all the time, and even have it rusted in open position, than have it close and by accident stay closed. That would be very bad news for your engine. Its supposed to be open when the engine is off. Then close when the engine starts up, and open up again as the engine warms up. Because its open most of the time, by now its probably rusted in the open position.
Leesburg, AL

"Cadillac Kid" Greg Surfas 15364

Scott,
Before you start plugging, disconnecting, revising, please pay attention to the usage of the car and your local.  These "smog" motors as designed are very sensitive to climatic conditions and inter-operation of the emission, ignition and fuel systems.  They can be quite cantankerous if miss-tuned.  IF you are going to do something like delete ANY of the components, I don't believe your customer will be satisfied with  the results unless you go back to all the systems and ;1. rejet and re calibrate the QJ, 2. revise the advance curve in the distributor, 3. revise the emission contol vacuum system to reflect that of the "pre" (what-ever you have deleted) component system. e.g. if you delete components and revise the advance curves it might be a good idea to replace the EFE sensor with the thermal controlled advance switch.  In my experience ALL of the emission, ignition and fuel control systems were developed emperically as a total unit by engineers who had the end product in mind.  These motors will run if all the parts are in the same zip code, but they only run WELL if all the systems are considered correctly.
Greg Surfas
Cadillac Kid-Greg Surfas
Director Modified Chapter CLC
CLC #15364
66 Coupe deVille (now gone to the UK)
72 Eldo Cpe  (now cruising the sands in Quatar)
73 Coupe deVille
75 Coupe deElegance
76 Coupe deVille
79 Coupe de ville with "Paris" (pick up) option and 472 motor
514 inch motor now in '73-

Scot Minesinger

Fairfax Station, VA  22039 (Washington DC Sub)
1970 Cadillac DeVille Convertible
1970 Cadillac Sedan DeVille
1970 four door Convertible w/Cadillac Warranty

R Schroeder

#16
Just to be clear, when I bought my car, I replaced all of the emission controls with new components.
I rebuilt the carb, and replaced all vacuum lines ,and electrical components, such as plugs and wires .....etc.
I went over the whole engine.
The only two changes I made were the EGR and the EFE, heat riser.
Carb was tuned in using a vacuum gage and tach, to obtain the highest reading.
78 Cadillac has 3 , maybe 4 different distributors that year.
Mine happened to be the one that has the most advance at idle, and cruising. 38 to 40 degrees BTC.
I personally don't have any problems with the way my engine runs.
As Greg says, some may need all the stuff on them to run correctly. I am not saying plugging off the EGR is going to solve your problem.
Anyone who owns an old car should go through everything on the engine to make sure its all up to snuff. Vacuum lines seem to be the biggest problem when you have 30 or 40 years on them.
One thing that always bothered me is when you pull the EGR and it covered with soot. To me ,that's what is going in your engine.
So, take it all with a grain of salt.
My engine pulls a STEADY 22 inches of vacuum , and runs out very nice.
Roy



Scot Minesinger

New information.  Owner says that after coil failed while driving at 70mph on highway.  The car backfired after car stopped running and ever since then this problem has been there.  Could the backfire have damaged the valve?, or is this an obvious thing I should know about?
Fairfax Station, VA  22039 (Washington DC Sub)
1970 Cadillac DeVille Convertible
1970 Cadillac Sedan DeVille
1970 four door Convertible w/Cadillac Warranty

TJ Hopland

Doubt it.  As said before if the valve was leaking it would not start or idle well.  At higher speeds you wouldn't notice if it was stuck open.

Has anyone checked to make sure the muffler has not been damaged?   Perhaps its got a major internal damage and now has a restriction in it?   Usually with a restricted exhaust they will start and idle well but just won't make any power and it will get worse as things heat up.
StPaul/Mpls, MN USA

73 Eldo convert w/FiTech EFI
80 Eldo Diesel
90 CDV
And other assorted stuff I keep buying for some reason

R Schroeder

T.J. brings up a good point. The exhaust system. You didn't say how many miles were on this car, or if it has those pellet filled catalytic converters on it. Those has a history of plugging up.
Roy