Engine wont shut off

I have a 1996 Ford Explorer. The engine keeps running after I turn the car off. I replaced the ignition key switch and its still doing the same thing. What else could be the problem?

How about a stuck on Relay!

The problem is likely the ignition switch rather than the key cylinder. The ignition switch should remove power from the "Run" circuits when the key is turned off. Any chance someone spilled soda or sugary coffee in the steering column? You might be able to just spray some contact cleaner in to the ignition switch and get another year or two out of it.

-Rod