1979 240D, 179k miles...... Its my parts car, been sitting undriven 6 weeks.

Took it on 70 mile spin today and the idle was high for the first 1/2 of the trip. It idled so high that I had to slip the clutch with my other foot on the brake at red lights to slow it down....... No such high idle situation had ever occurred before it was parked in January.

But then it miraculously calmed down and resumed idling at normal speed for the return trip!

There is no alda, weird vacuum/electric fuel and air regulating device or crazy oil separator breathing apparatus on this '79 240D. There's no cruise control and nothing looked sticky with the throttle linkage or idle adjust. Fuel is ordinary truck stop #2 diesel. And the vehicle has no maintenance issues re/ filters, valve clearances, etc....... What caused this *temporary* high idle situation??

I wonder if the valve adjustment could affect it? My folks' '79 240D had a high idle until the valves were adjusted.

__________________
1979 300D 220 K miles
1995 C280 109 K miles
1992 Cadillac Eldorado Touring Coupe 57K miles SOLD
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1979 240D 140Kmiles (bought for parents) *SOLD.
SAN FRANCISCO/(*San Diego)
1989 300SE 148 K miles *SOLD

Yeah but how did it suddenly heal itself?