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MB Paul
MB Paul, Mercedes Technician
Category: Mercedes
Satisfied Customers: 3567
Experience:  Qualified Mercedes Benz Diagnostic Technician - 20+ years experience - Workshop Foreman for Mercedes
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Marty, I wanted to let you know what became of this issue.

Customer Question

I wanted to let you know what became of this issue. Continued to have traffic light, rough idle and surging, no codes, not messages. After all the parts I replaced and diagnosis that was done, I finally took it in to be smoke tested again. Come to find out, the new dealer EGR valve was no good. It was leaking. I put the 2nd EGR valve on about a month ago, no issues since.
I guess the theory of it is, since it already had a vacuum leak, the computer was compensating, when the evap system purged, I guess the ecu leaned it out? Anyway, I wanted you to have the solution to this, after spending so much time helping me.
Besides, I have another car I'll probably need your help with before too long.Thanks,
Submitted: 10 months ago.
Category: Mercedes
Expert:  Marty replied 9 months ago.

Hi Chad, thanks for the update. I'm glad you got it sorted out. Some of the most difficult ones to diagnose are the ones where the new part is defective.

Let me know if you need anything.