I finally got around to checking the duty cycle at the diagnostic port (round thing with a screw cap on left inner fender) using the no. 2 (-) and 3 (+) pin connection.
I tested the Ign. on / Eng. off test and got 70%. Then tested with engine running at operating temp and got 50.4% at idle with fluctuations at higher RPMs.
Using a 3 mm Allen key - pushing down to engage the adjuster - turned it CCW from 12 o'clock to half way to 11 o'clock. Waiting 10 seconds - the idle duty cycle was now fluctuating between 42 to 49%. I did a few more very very small adjustments but ended back at the first adjustment. This thing is super sensitive. I could not have done this without my Fluke 87V.
After all these years will a slightly high idle and stumble starts from a stop it finally has a normal idle and strong off the line. Amazing how that small adjustment made such a huge improvement. This also fixed the RPM hunting on deceleration.
off topic. I noticed outer rubber on one of the fuel lines is dry rotted. The inner plastic line is not leaking but need to be replaced asap. This is the one that goes into the fuel distributor and routs to the inner fender and down under. (Not the chilled one) Looks like a PITA.
I think the PN is 1264703675. I found the number on the Mercedes of South Atlanta parts site.
Where should I buy one from and how hard is it to replace?
Thanks,
Rich