A few weeks ago i started my car at work to let it warm up and when i got in to leave, i put it in drive and the idle dropped to approximately 600rpms and it started to shake like it was gonna stall. I didnt have any more problems with that up until 2 days ago when it started again and now its not going away. When you cold start the car it runs close to 2000 rpms then it drops to 1000 when its warmed. But once i put the car in drive it drops to 600-650 and it shakes a bit. You can also hear it in the exhaust like its running on 5 cylinders. I did a bit of research and ive removed and cleaned my IAC valve. There was no change in performance. But once i pieced it all back together and started it, it threw me an engine error code, which it hadnt done previously. The print out from the computer was "Cylinder 1 Missfire". Now my next step is to change my plugs but could this also be a bad injector? Would that also give the same symptoms ive experienced? Any thoughts?
Edit: Exact from OBDII printout
"
DTC (Codes)
P0300
Random/Multiple
Cylinder
Misfire Detected
P0301
Cylinder 1
Misfire Detected
DTC Pending (Codes)
P0301
Cylinder 1
Misfire Detected "
The only thing that worries me is that it didnt throw a code until i pulled it apart and cleaned that valve. So im wondering if the error code is from the initial start up when i put it back together.