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This is a classsic symtom of the TSB by Benz on changing the EGR vave to the new style..
The old ones were sticking open, and this not only causes CE lamp, but a vac leak at idle [ when the ECU actually disengages the egr system]
If the dealer has checked/changed the valve to the new style, they are supposed to put a RED paint drop on the valve per TSB.
One wants to remember that the DIFFERENCE in diagnosis of a code for EGR between air tube blockage and a sticking EGR
are that one is not allowing exhaust recirculation [ blocked] and the other is allowing it when it is not supposed to be [ sticking valve]
These will BOTH bring up the egr code, so the test is to apply vac w/hand pump at the egr SOV hose port and pull some vac to manually open/close the valve ..
If there is blockage at the tube end , the engine will not show a significant rpm change at idle.. if it does , then you know you have vac flow throught the tube[ very rough running condition w/test]
I like to hear a nice "Snap" closing when releasing vac with this test....
Because the blockage of the egr tube is so common, many believe that the EGR itself is not at fault, but that is not the case ..that is why Benz re-designed the part and put out the TSB
Anyone needing that TSB/info is welcomed...
Last edited by Arthur Dalton; 05-22-2003 at 01:14 PM.
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