The leading causes of misfire at idle are bad ignition wires (and cap and rotor) and vacuum leaks. Check the idle control valve hoses (probably rock hard and leaking), boot between the air flow meter housing on the fuel distributor and the throttle body, and injector seals along with injector sleeve seals.

Injector seal leaks will cause bad idle because the computer and fuel distributor cannot control the mixture properly. Sadly, excess valve guide clearance will also cause serious idle problems for the same reason -- unmetered air so it runs way too lean.

A bad OVP relay will also cause rough idle, so will a bad fuel pump relay!

Peter

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1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!