I have a 1986 190E 2.3-16, Euro model, with a 5 speed and the factory US style emissions system installed. The car has over 200,000 miles and runs strong, lor burning a quart of oil every 3,000 miles. Anyway, I live in Connecticut where there are emissions tests required every two years and I just passed by the narrowest of margins on HC and CO, which is a degradation from earlier years. It also runs rough at 2300 to 2700 rpm when it is cold, and gives off a little black smoke and stench of unburned fuel when cold. The smell and black smoke is reduced at normal operating temps, but it still is apparent even warmed up. The mileage has dropped from arund 25 to 28 mpg, depending on how much and how fast I drive the highways, to around 20 mpg to maybe 22 mpg.

My question is, how do you adjust the mixture? Is it adjustable?

The injectors are the original injectors, plugs are less than 20,000 miles old (Bosch Platinum 4), the air cleaner is relatively new (8,000 miles, no visible debris). It is normal to see some reduction in mileage when the weather turns colder, but this year has not been a normal year. If it was 20 degrees out all the time, I would not be as concerned, but it has been in the 40 to 70 degree range, which is not cold weather.

Any suggestions? Thanks, Jim

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Own:
1986 Euro 190E 2.3-16 (291,000 miles),
1998 E300D TurboDiesel, 231,000 miles -purchased with 45,000,
1988 300E 5-speed 252,000 miles,
1983 240D 4-speed, purchased w/136,000, now with 222,000 miles.
2009 ML320CDI Bluetec, 89,000 miles

Owned:
1971 220D (250,000 miles plus, sold to father-in-law),
1975 240D (245,000 miles - died of body rot),
1991 350SD (176,560 miles, weakest Benz I have owned),
1999 C230 Sport (45,400 miles),
1982 240D (321,000 miles, put to sleep)