[SteveSarre]

Hi Malcolm,

Frustrating.

Just 5 ideas:

1.
Have you checked or replaced spark plugs, ignition wires and distributor cap and rotor?
Maybe when the engine warms up partly, but not fully, one of those components is on its limit.
Original Volvo ignition wires have the week and year of manufacture on them. They don't last forever.

2.
Sometimes the electrical connector block on the back (LHS) of the ignition lock becomes erratic. See if wiggling the key helps next time it happens.

3.
Wild guess, check the condition of your battery cables near the battery, positive and negative.

4.
When it next runs rough, after stopping the engine first, see which cylinders are NOT contributing to the rough running, by pulling the HT lead off the spark plug or the distributor cap, one at a time. Or do it while the engine is running but you might get a shock.

5.
When you turn the ignition on, before starting, you should just be able to hear the fuel pump whirring for a few seconds (near the spare tyre well).
If it doesn't whirr, and the car doesn't start, then that needs to be looked at.

Steve