If you have a meter that is capable, I have written how to check lambda with a FLUKE 87...You can search and find it. You are looking for a reading of about 50% at idle with less than a 10% deviation at 2,500 rpm

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Benzmac:
Donnie Drummonds
1992 500E (very soon I hope
1981 280GE SWB
ASE CERTIFIED MASTER AUTO TECHNICIAN
SERVICE MANAGER FOR 14 BAY FACILITY
MERCEDES SPECIALIST 8 YRS
PARTNER IN MERCEDESSHOP.COM