HI NIKOS124,
I am quite positive , the idle control unit is the culprit. It just behind the electronic fuel distributer
ZEE

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1990 220TE
1988 300GD
1989 yamaha V-MAX(sold)
1993 BMW R100R
1956 Willys Jeep(low bonnet)
1982 Honda XL 250
1987 300D
1994 toyota surf (4runner)2.4 TD EFI
1953 Land Rover