my 87 syncro has been running fine and all of a sudden lately after sitting awhile 2 months it has a problem.

When I first start it seems ok, as it warms up a bit it starts to miss and run very badly as if I have a set of wires crossed. I tried shutting off the ignition and waiting 30 sec and restart but same. It seems to cut in and out and surge like water in the ignition or fuel?

Came out of the store hopped in and it ran fine. 

Any thoughts?

Thanks

Doug