My son attempted a PI manifold swap the last couple days that ended with figuring out the manifold was a POS. So we threw the original manifold back on. When we started it the engine sounded like it has a cam. I pulled the codes and one was P0117 I think. Coolant sensor circuit low or something to that affect. I noticed the fan kicks on a few seconds after starting the engine. Would a bad sensor cause a crappy idle? If so any way to figure out which one it is?