Dear B.B.,

Hope you're well. For a car nearly 30 years old, intermittency likely results from worn-out relays and/or corroded electrical connections of those relays. Sometimes an invisibly-thin layer of corrosion - a few molecules thick - suffices to disrupt smooth operation. When connectors are corroded, changes in heat and ambient humidity suffice to disrupt the flow of power.

As your car has a turbo, it has Bosch fuel supply and management. So, there's an in-tank pre-pump and a main fuel pump, mounted on the under-body, approximately under the driver's seat. These pumps are pretty robust, so should not be an issue, unless the car has lived in the salt-belt or near an ocean. If so, then the main pump's electrical connections should be inspected.

Thus, I'd replace: (a) the fuel pump relay (white rectangular unit, mounted on the main relay panel behind the front, center console's ashtray; (b) the fuel injection relay (also known as the radio interference suppression relay) dark-brown, mounted in the engine bay, on the inner fender wall, to the rear of the driver's headlight; (c) the ignition power stage (flat, with a gray cap, engine bay, inner fender wall, to the rear of the passenger headlight).

If these steps do not end the problem, then look at: (a) the distributor cap/rotor and (b) the ignition coil, a cylindrical device (black or aluminum casing) mounted on a strut tower. The distributor cap/rotor should not be - and likely are not - factory-original. But if moisture gets into the distributor cap, rough-running would not be surprising.

Use an aerosol corrosion-remover, e.g., Deoxit, to clean the wiring harness connectors.

Key point: the parts that I suggest be replaced - if factory-original - are going to tail sometime soon because they're at or near the end of their service life. Thus, the replacement cost is going to have to be met sometime soon. Replacing them - and cleaning the wiring harness connectors - ensures smooth operation for a long time.

Hope this helps.

Yours faithfully,

Spook