87 integra tach

car has stock tach and it bounces wildly at idle, then smooths out and is accurate while driving. any help thanks

I have an 88 Integra and had the same problem, but at 4-5 rpm's. It could be your rotor and/or the timing. Some Acura friendly shops will check the timing for free. As for myself I changed the rotor, distributor cap, wires, spark plugs and had the timing set. Problem solved. Although, I would get a second opinion from one of the moderators or enthusiasts.