I have a 98 Dakota with about 240K on the clock. Everything has been done to try and keep it in top running order. Every once in a while I would get a hiccup like an engine miss but never any codes. My question is this...would the PCM actually pick up an engine misfire if say there was water or some other contaminant in the fuel? Let's say the plug fires and the PCM picks up the necessary current saying the plug did fire but the actual fuel wasn't really fuel? Could this be a reason a code may not be set? The reason I ask this question is that now I'm using a midgrade fuel, it doesn't happen anymore....it runs strong and idles smoother? Has anyone else ever experienced this? No pinging ever with regular but runs different with midgrade. I always thought the PCM would make the necessary adjustments n o matter what fuel you would use. Thanks for any experiences out there with fuel.