1992 240 automatic. Has fresh tune up.
Last year I tried to resolve this issue, and finally wound up with an electric blanket on the engine every night. Works fine, but... besides it have expanded
to damp days hard starts. And it isn't even cold yet. Once the engine starts it continues to run ok, although extra gas may be necessary at stop lights. What would cause this that a warm blankie fixes?

This may be off the wall, but I got it from an independent Volvo tech with years of experience here and in Norway. He says this symptom (which blooms in the Fall each year) can be due to accumulated deposits on the intake valves and in the intake valve area.

The theory is that these deposits soak up a portion of what the ECU intended as extra fuel for cold-running. After a few minutes, as the deposits become saturated and the engine warms a bit, the mixture then becomes adequate for the conditions.

He didn't have a quick fix, except to run some straight Techron or maybe BG44K through the fuel system. More than once probably.
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Bruce Young
'93 940-NA (current) — 240s (one V8) — 140s — 122s — since '63.

What shape are the ignition wires in? The energy intended for the spark plug will find an alternate route along the wire jacket if they are in poor shape and damp. Is there condensation inside the distributor cap? Same thing happens in there. Is the top of the ignition coil and outside of the cap clean? The spark is more likely the short out when things get a little damp. Something to think about at least.