need help with nissan problems

i havent drove my truck for about 3 months but i would start it up and let it run for a little bite here and there.It is a 87 nissan hardbody Z24 when it runs know at ildel it ideals up and down does anybody know how to fix it or any ideas.The truck does not have an ideal position senser on it thanks

air flow meter, my 87 started doing that same thing one day after sitting for a long time.

might want to check your vaccum lines