Hello everyone, I'm asking this question on behalf of my dad so I don't really know much about cars or what he's done. If the details I provide aren't enough though feel free to ask any questions and I'll try to find out from my dad.

So anyways, the problem is everytime he starts up the engine it just starts overrevving, like as soon as he turns the engine on. He just changed the spark plugs, spark plug wiring, the fuses, and did something with the Intake Air Valve or Header (I don't know exactly what he said) to correct another problem, and now this problem has come up. So I'm going to assume it has something to do with that, but I don't know exactly what it is. Any help at all would be greatly appreciated.

Also if it helps at all it's a 2000 dodge caravan, automatic transmission, FWD, 3.3L engine, and 125K miles on it.