Things to check would be the Idle air control valve. There is a port which gets occluded with carbon, the whole throttle body might need a good decarboning.
If there are weird issues also occurring regarding the electrics, it is wise to unhook battery connections, look for green and white corrosion wicking up under the wire insulation. If present a simple cleaning of it might not help. Don't be too quick to dismiss the battery cables as culprits.
Also follow the - wires from battery - to firewall and to engine block, remove, make shiny retighten.
One other known issue is the connections at the engine computer.
The presence of dieelectric grease inside theese connectors, does not mean all is well inside, and the weight of the wire bundles hanging on these connectors can break the solder joints on the pin connectors and lead to very strange intermittent issues once the wires all heat up and present just the right amount of stress to the broken solder joints.
Flushing out the old crusty dielectric grease with a nice spray can or CRC qed cleaner is not enough to remove oxidation from mating conductive services.
If the solder joints are broken then this cleaning will not fix that, but it will likely change when and where it acts up. It might even go away for a few months only to return at the most inopportune time.
Caig Deoxit d5 spray has no equal in this regard( cleaning conductive surfaces) but it is too expensive to use it to flush out old di-electric grease. The mini dental brushes sold in drug stores, can help dislodge grease and clean, the Deoxit d5 or d100 if really oxidized, can make dull oxidized silver look like polished silver, and new Dielectric grease will prevent the oxidation from returning quickly.