P0304 code

[calla1231]

97 lx escort wagon, 169,000 miles 5 speed
a few weeks ago my car started acting like it was about to die when first cranked(idle dropped down, sputtering). after about 45 seconds or a minute it would clear up but it threw codes P0301-p0304. it would do it randomly, sometimes first crank of day, sometimes after it had been running for awhile. we replaced the wires and plugs, didn't fix it so we went with a new coil pack. that cleared everything up and it ran fine for about 2 weeks then 2 days ago it started again. this time it throws code p0304(cylinder 4 misfire). again, it is random when it does it. also, the canister purge valve solenoid was recently replaced too along with a camshaft position sensor back in april. I thought maybe a bad injector but I did an ohms test and they all read ok, and I did the click test(feeling for the click in each one when running) and they were all clicking. any ideas?

[zzyzzx2]

http://www.obd-codes.com/p0304