Well, failed my Illinois emissions test. Vehicle is 1984 500SEL euro model. The car did have catalytics spliced into the system when it was brought over, and this version has no lambda adjustments possible. Illinois does a simulated city/highway drive and unfortunately provides their numbers in "GPM", not %. Any help on how to convert would be extremely helpful. The O2 sensor was messed up so that caused pretty bad readings. Not sure why I took the test in the first place, I knew it was idling a bit dodgy. Oh well on that one.

Anywho, I replaced the O2 sensor, plugs, wires, did a fresh oil change, and double checked the lambda %duty which is reading what to book says, though I can't change it anyway. The sensor cable was buggered up so I replaced that all the way into the box. I'm doing the retest tomorrow. At this point the car idles and runs as smooth as it ever has so I'm crossing fingers.

Question is, has anyone had an 80's euro model pass emissions test in Illinois lately? I'm wondering if this model will pass the fancy test at all. The limits they give, for whatever it's worth, are HC max 2.00 GPM, CO 30.0 GPM, no limit on CO2. I don't even know how they measure GPM on a complex mixture of HC in the first place. Must be interpreted some how.