Need some minor help. 86 tercel idling rough

I could use a little help on this one. I just bought this car, and the motor idles a bit rough, like it will idle fine, then just drop like it wants to stall, then back to normal idle again. at speed its just fine, but when sitting at a stoplight, it'll do the weird idle mentioned above. I dont know it could just be old fuel, it could be plugs, I just dont know.

Does anyone have some advice on this? I'd like to have it running nice, because I like this little car.

Start by servicing the car. Tune-up, fluid changes, inspect everything especially the vacuum hoses, use a fuel system additive and top off with premium gas, put couple of hundred miles on the car and see if it improves.

Mine does that after plugs, wires, new belts, cap, rotor, fixed the exhaust leak, re done the vac lines, and cleaned the IAC valve and the idle is still real rough, espically when its in drive.