1999 Voyager won't idle

My husband and his best friend changed the oil pump in his friend's 1999 Voyager with a 2.4L engine. They got everything back together and now it won't idle. It cranks great, runs great on the highway, but when you take your foot off the accelerator, it dies. HELP!!

I know little about the 2.4 but I'm thinking a disconnected vacuum line. If you pulled the timing belt or chain maybe it's off a bit. Damaged IAC valve/motor connection?