My gauges come and go occasionally, but today (on startup) they all went out except the speedometer... which fluxuates between 20mph and pinned. Idle sounds OK, but when I step on the gas it hesitates and keeps stuttering. Undriveable, if that's a word. I'll take a closer look this evening, but where to start? The exhaust is rusty, but I don't see an O2 sensor messing with the speedometer. Battery is a three year old red top. Ambient temperature this morning was 40F. XJ is a DD and was last run Friday night - no problems.