How test EGR valve? - Mercedes-Benz Forum

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post #1 of 2 (permalink) Old 03-30-2012, 12:58 AM Thread Starter
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How test EGR valve?


Is there a way to test an EGR valve? I just (barely) passed CA smog with my 1990 300SE -- NO at 529 at 15 MPH just under the limit. I've replaced the catalytic converter and the oxygen sensor.


-- Roy Zider

1990 300SE 154,791 miles

15	1795	14.7	0.3	88	0.18	529
25	1863	14.9	0.1	50	0.05	106

1990 300SE
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post #2 of 2 (permalink) Old 04-01-2012, 02:15 PM
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I can't recall or not but that egr should be vacuum actuated. You can unplug the vacuum line and hook up a vacuum pump to it. with the car at idle apply vacuum to the valve and see if the vacuum holds. If it holds you know the diaphragm is intact. With vacuum applied the idle should be really rough. if the idle does not get noticably worse then the passages are probably plugged up with carbon. you can take the valve off and clean the carbon out and retest it. Hope that helps
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