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Old 08-12-2001, 05:15 PM
JimSmith JimSmith is offline
Join Date: Jul 2001
Location: Old Lyme, Connecticut
Posts: 3,596
190/16 Valve A/C and Engine Idle Stability Is Intermittent

Hi, I hope someone can help me out here. My 1986 190E 2.3-16, a grey market vehicle I imported new in 1986 and have used as daily transportation for the last 15 years now has 199,450 miles and still runs strong. I recently started using a lot less oil, and get around 2 to 3 miles per gallon better mileage, so I think it is really breaking in, finally. When I got it new it used about a quart of oil every 1,500 to 2,000 miles and got 23 to 24 mpg. Today it uses no oil between oil changes (3,000 to 3,500 miles, always synthetic, either Mobil 1 20W50 or Castrol Synteck 5W50) and gets up to 27 miles per gallon. So the machine is in relatively good shape.

Around 110,000 miles ago the idle control died, and the car would stall all the time. I had the "idle-motor" on the intake manifold replaced and the problem went away. The new one was significantly different in shape than the original part, but it fit and works great. Until last summer, when the car began to idle at a high rpm most of the time. Some times the the idle would be normal (900-1100 rpm) but for the most part it would be around 1500 to 1800 rpm, regardless of the engine temperature. This had no significant effect on the mileage.

Then, also last summer the A/C would decide on its own when it would be on. The factory A/C in this car is the manually controlled variety as the fancy climate control system was another $2400 and for that kind of cash in 1986 I felt turning the A/C on and pushing a little lever to control how cold it got was a better deal. The intermittent A/C operation is becoming more off and less time on these days, and I cannot figure out where the problem is. When the A/C is on, it provides good cold air, so I do not think the freon charge is the issue.

I have been reading threads mentioning the overvoltage protection relay for this car having some control over the idle and the A/C operation. At present the idle seems ok, but the A/C is still acting up. Any clues?

I also noted the auxiliary fan hardly runs, if ever. It is not siezed, but I have not heard it lately and when I run the car hard in hot weather, or get stuck in traffic idling, the car heats up pretty good. There is a resistor mounted on the driver side inner fender that has some corrosion on the connections, which I will clean off today, but is there a resistance value for this item I can check?

Thanks for any ideas. Jim
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

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)
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