Ford Freestar Van woes

I own a 2004 Freestar van that I use as a delivery vehicle for my small business. It has started to run rough whenever the weather/air gets damp - rain, high humidity cause it to chug. Trying to accelerate the RPMs go up but the van hardly moves. When you’re sitting at a light it acts like it’s going to stall. I have taken it to several mechanics,who all replaced parts they claimed were the problems, been charged ridiculous repair costs and it is still running the same. HELP I can’t afford to buy a new vehicle but can’t afford to keep dumping money on repairs that don’t fix the problem!

When was the last time the spark plugs and more specifically…the plug wires were changed? When plug wires go bad they create havoc with the engine when the air is damp. If they have been changed then it’s most likely an ignition component.