I recently purchased an 04 PT cruiser,2.4 non turbo version. Car ran GREAT when I first got it,it said it needed o2 sensors at first. Now I have 2 misfire codes,and an open loop in injector 4 code. I've replaced plugs,wires and coil pack and I didn't want to go any further without asking around first.

 

When you replaced the O2 sensors what brand did you use? Chryslers prefer NTK, Denso or OEM O2 sensors. They do not usually like Bosch.

For the spark plugs, did you use copper plugs? Champion or NGK copper plugs work best. There have been issues reported with platinum or iridium.