1997 Chrysler LHS Trouble Codes

My check engine light came on awhile back I was told I needed new spark plugs and new injectors and other things. These were all replace and with 100 miles it was back on. I bought my own reader and first it said there was misfire on number one but it was firing, then later on it said the injector wasn't working. Then after I tinkered with it it changed to saying number two was misfiring and the injector wasn't working. I ran diagnostics cleared codes and drove it awhile. The light came back on and said that number one and two were again not working, that the idle was wrong and there was transmission failure. I parked the car for about four months and then decided to work on it again. I cleared all those codes and the light didn't come on for about 25 miles then it came on and said that number three was misfiring and the injector wasn't working. I cleared that code and after about five miles the light came on but the reader said there was no misfire. Now it alternatly says there is a misfire or there is no codes even if the light is on. Is this a PCM problem or what?