acceleration and idle jumping on 96 civic

I just bought a 96 honda civic, and when I'm in park the rpms jump around
from 0-2000. If I'm at a complete stop and take my foot off the brake,
the car will accelerate to 20 mph, then drop to 10, and continue jumping
up and down. The rpms jump between 2000-4000 by it's self. last night I
drove 3 blocks home without ever putting my foot on the gas!!! Is this
normal??? What is causing this?

 

There are a couple of common problems that can cause those symptoms.

1. Low coolant or air pockets in the cooling system. Most Honda engines
require a fairly elaborate bleeding process when filling coolant. If you
have air pockets, you can get situations where sensors and valves are
not immersed in coolant and thus thinks the engine is at a different
temperature than it really is.

2. Vacuum leaks, allowing excess air into the intake manifold.

What engine do you have? Manual or automatic?

 

it's automatic....about the coolant issue...I had to have the radiator
replaced when I bought it...they put in the new radiator and put in the
coolant, and that was it!!
Could this be the problem??