Strangest thing happened today. I have a 98 Grand Cherokee 5.9 with about 175k. I have only owned it for about 6 months. So, I started it for the first time in several weeks and it immediately died. Starts just fine but I have to keep my foot on the gas to keep it running. It doesnt "sputter" out....it immediately drops to 0rpms once I take my foot off the pedal. The wierd this is that all settings reset (i.e. Radio) as if the battery died. Also, the gauge cluster lights dimmed in and out as I held it at about 2000 rpms. I did not drive it....just locked her back up and went inside. Any ideas? Thanks.

 

Your battery is junk. Replace it and start the engine. You will have to keep your foot on the gas for a few minutes until the ECM relearns the idle setting.

 

x2 on battery. My died in this last month and had the same exact symptoms on start up.