Have same problem on 04 neon. Check fuel, and ignition along with valve cover gasket with spark plug tubes and seals. If problem is not found here, while valve cover is off, perform a compression check. My No. 3 cyl was low (60 psi) I next removed the intake and exhaust rocker shafts, pressurized the cylinder, and air escaped out the tail pipe. Checked the other cylinders and they were good. I then
tapped the exhaust valves with a plastic hammer, hoping to loosen some stuck carbon. No good. Hope this is not your problem, but this was mine, a burnt exhaust valve.