93 190E with 2.3 eng. has rough idle. Replaced plugs and one resistor tip, which smoothed idle a little. I then decided to check voltage at the diagnostic socket. With key on engine off I am only getting 1.83 volts. With engine running I'm getting 13.85 volts. Duty cycle gives me OL on my DVM. I decided to replace the over voltage relay, which didn't change my readings. The literature I have, says there should be 2.5-5.0 volts koeo and should be around 6.5 volts with engine running. There are no faults stored when checked with scanner. What else could cause these symptoms if its not the OVP? Any suggestions are appreciated.

The 1991 & later 2.3's need to be put into diagnostic mode before you can read the DUTY cycle at connector.

Also, search for Lambda and see what you get. I posted a message on this a while back on how to read lambda with a DVOM.

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Benzmac:
Donnie Drummonds
1991 GMC Syclone
ASE CERTIFIED MASTER AUTO TECHNICIAN
SERVICE MANAGER FOR 14 BAY FACILITY
MERCEDES SPECIALIST 8 YRS
PARTNER IN MERCEDESSHOP.COM

Thanks for the replies Benzmac and M.B.DOC.. I am using a fluke 88 DVM so the procedure is a little different than the 87 but the information is very helpful. How do I put the car in the diagnostic mode, that M.B.DOC suggested? Again thanks in advance for any advice.