My 85 380SE (198k) idles at about 700 in P but drops to just above 500 in D. It idles smooth in both, has normal power, etc. Any idea what to look at? The only reason I care is that the temp goes up at a stop after freeway driving unless I put it in P while I'm stopped esp with ac on. TIA, Jim

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85 300 SD ~ 115K
82 500 SEC Euro ??K
78 450SL 164K

it would be normal for it to drop some. 200 rpm seems a bit much.

tom w

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

Do a search on idle control valve. They get dirty over time and can affect your idle. Normal idle in drive is around 600, so yours is not way off. The auxiliary fan might not be working.

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1985 380SE Blue/Blue - 230,000 miles
2012 Subaru Forester 5-speed
2005 Toyota Sienna
2004 Chrysler Sebring convertible
1999 Toyota Tacoma