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  #1  
Old 03-26-2001, 11:25 PM
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I have a beautiful 1995 S-350 that I would like to keep forever. I do not think it will last very long sucking in all the crud from the EGR valve. I do not know the workings of this valve in relation to the engine computer, but when I plug the vacuum line at the EGR valve or the thing before the valve and drive the car 2-3 miles it looses power until I hook the line back up AND restart the car. I guess this resets the computer. What is being sensed and where to tell the car not to (I think) give full turbo boost. I want to disconnect this valve even if it means routing a new line to the air filter housing and welding a plate over the exhaust manifold hole for the EGR pipe.




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  #2  
Old 03-27-2001, 05:03 PM
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I have some more information to add on the EGR. There are two vacuum transducers- one for the egr and one for the boost pressure. There is another valve called a boost pressure cut-out switchover valve that should a malfunction occur in the boost pressure control circuit, the valve vents the boost pressure and the injected fuel quantity is reduced. I think this is what is happening. There is a two lead wire going to both transducers and to the cut-out switch and to another valve right at the egr. What is telling the car to cut boost when the vacuum line at egr is plugged and how do I trick it into thinking nothing is wrong?
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  #3  
Old 03-27-2001, 06:06 PM
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I'm not familiar with your EGR valve design, but maybe all you need to do is put a blocking plate between the EGR valve and the manifold. The EGR system will continue to function, but exhaust gas won't recirculate.

This suggestion, whether it works or not, is not intended to help anyone violate any laws or regulations.

Sixto
91 300SE
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  #4  
Old 03-27-2001, 06:23 PM
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Thanks sixto--I had thought about that but wasn't for sure. I am not trying to break any law, but I want my engine to last and I don't like the intake getting stopped up like it does.
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Old 03-27-2001, 06:39 PM
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Now that I think about it, I had a 91 Mitsubishi that had a temp sensor on the EGR valve. The temp sensor or EGR valve went south and caused a check engine light. I don't think there was a change in performance. The point is that if your car checks the temperature at the EGR valve, it may notice that you've blocked the passage. But I think it's such a simple thing to do yourself that it's worth the exercise.

Sixto
91 300SE
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  #6  
Old 03-27-2001, 08:43 PM
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Your engine has a sensor on top that tells the computer whether or not the valve is opening...IF you try to fool it, you'll set a light.

Sorry.

No fooling this one.
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  #7  
Old 03-27-2001, 10:22 PM
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Benzmac--Exactly where is this sensor and what does it sense. I have found one line comming off of the intake runners that goes to a little square thing part # 011 542 07 17. Is this the sensor and if so what does it do or sense. There is bound to be a way. You sure the plate idea between the egr valve and the housing wouldn't work?
Thanks

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  #8  
Old 03-28-2001, 02:24 AM
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smoke gets in your eyes
 
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If your engine is anything like the one described in the 91 350SDL section of the W126 CD manual, it seems that fitting a blockage between the EGR valve the mixing pipe is a mechanically trivial proposition.

I don't know what kind of sensor can verify that exhaust gas is actually flowing into the mixing pipe, but that doesn't mean there isn't one. Benzmac's statement implies that MB really doesn't want you to disable the system.

If you're concerned about crud entering the intake manifold, consider that the PCV system might also contribute to the mess. On mortal cars, it's easy enough to fit a generic fuel filter to serve as an oil trap. Or there are devices designed specifically for this purpose. Unfortunately, MB has huge PVC pipes that don't lend themselves to easy fitment of an oil trap.

Regards,
Sixto
91 300SE
... emission control devices in place an operating AFAIK
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  #9  
Old 03-28-2001, 07:04 PM
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Update--I made a blocking plate and put it between the egr and the housing. Still something cut the power (cut boost for sure, maybe fuel also). I called a service manager I know and his only advice was to bypass the turbo boost pressure valve-- He said it is the one beside the intake manifold. Connect the two vacuum lines together. Only thing if an overboost condition was ever to happen, it could fry the engine (what he says). Still don't know if that would completely solve the power issue.

I just don't know how the engine knows that it is not getting egr. I cannot see anything downstream that could be sensing it. Maybe it could be the airflow meter upstream that is telling the computer that more air is flowing past it because it is not getting any exhaust air.

Any thoughts anyone!



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  #10  
Old 03-28-2001, 07:37 PM
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The next thing I'd try is to vent the EGR valve to atmosphere (bad Sixto; bad, bad Sixto) or back into the exhaust tract. You might experiment venting to atmosphere very very briefly to see if that fools the sensor. Don't forget to plug the EGR valve flange on the mixing pipe.

You could also try to plug the exhaust end of the EGR valve while keeping the mixing pipe end open. It's a long shot, but since you don't know exaxtly what the sensor is looking for, it's worth a shot.

If you bypass the overboost protection circuit, you can attach a pressure relief valve to the flange in the mixing pipe. There are numerous after market relief valves for turbo applications (Mitsubishi, Audi, VW). You'll want the type that's adjustable so you can dial it in to the stock overboost level. It won't provide the backup of cutting fuel, but it's better than nothing.

I'm not a fan of a solution that doesn't address the engine fault light.

Sixto
91 300SE


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  #11  
Old 03-28-2001, 11:53 PM
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No check engine light in the car that I know of. None comes on when I loose power. Would like to know what is being sensed and where. I have to run it down the road a mile or so before the power gets cut. Thought I had it with the blocking plate but wham, no power. I guess the Germans engineer the emissions controls like they do the rest of the car! About ready to give up. Exactly how does the boost pressure control work. I think there is a boost pressure control vacuum transducer, a boost pressure cut-out switchover valve, and a pressure sensor, but I don't know the workings of the system. Repeat-- I am not interested in the engine light cause I don't have one.
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