Why is RPM to high on `93 Chrysler Voyager?

Can anyone help me with my problem?:
I have a 93 chrysler voyager which i recently changed the spark
plugs to, and i have checked and recked that everything was put back &
plugged correctly, however, whenever i turn on the van the idle is to
high, and the r.p.m. rises above 3,200 on Park. It lowers only about
400 r.p.m. whenever i put it to Drive and about 600 r.p.m. when i put
it in Reverse and it stays at 3,200 if i put it in Neutral. The r.p.m.
is way too high and i don't know what's wrong with the van. I've
checked & recked everything making sure that every cable, plug, &
component was in correctly, but it is still too high! I can't figuire
it out and would like to know why the idle is too high. Can anyone
please help me with this problem?

 

Sounds as if you have a vacuum hose off, such as the brake booster hose or a
gasket leak at the intake or throttle body base