A smelly question about a Ford Five Hundred

For the last week my 500 has been reving up and tring to lurch forward when I’m stopped at lights. Then yesterday when I let it idle while I ran fresh water for my horse it reved up high like someone stomped on the gas and then it shut off. When I backed under the carport it reved up again and I almost hit the lawnmower. This morning when we started for church and turned on the AC it smelled like something had craweled up in it and died some time ago. Any ideas? Oh, Everything else happened with the AC running, too.

Whenever the A/C is on the engine rpms increase to compensate for the extra load.

The signal going to the computer (BCM or PCM?) may be confusing and is causing the engine to race. At any rate I suspect an electrical glitch.

The techs here will be able to help better.