1991 Mazda MX5 I think idle is low

When I start my car it starts fine and then it gose to about 250 rpms, and the engine almost dies, then it gose back up to about 800 rpms, it will not idle higher. If I rev when in nuteral it goes up fine but then it goes back to about 200 rpms and almost dies. I changed the spark plug wires, and if I feel one of them above the spark plug I can feel it ticking, the others dont do that, and I can hear that one ticking farly loud. If I replace the spark plug do you think it will fix my idle problem? Or do most manual cars do that?
thanks chris.