2005 Kia Spectra • 4 cylinder • 97 miles

After engine has completely warmed up (15-20 min of driving)the car****** very roughly at the 22mph mark. The RPM gauge also revs at the same time. This will only happen if I am accelerating. For example, if I take my foot off the gas and let the car coast over the 22 mph mark, it will not*****. A free computer scan gave a code of P0304 cyl 4 misfire. Any ideas?
January 8, 2011.

Since you know the #4 cylinder is missing, I would start there. Change the plug and wire. If that doesn't fix the problem, have compression checked on that cylinder. Also, make sure the injector is working all the time.