1991 Jeep YJ • 114,000 miles

My jeep is a 91 yj wrangler 4 cylinder, 5 speed, 4x4, with 114,000 on it. I think I have a couple problems. The engine temp gauge will go from 0 to 260 in a few minutes while the heater is still blowing out cold air. It has coolant and I did a thermostat about a year ago. While driving it sits up around 250 then drops to 220 and in a second will go immediately back up to 250. Think it is a sensor? Also, after each time I shift it is like it has no power for a couple seconds and then it is fine, but only while the engine is cold. Today I went to drive it and stalled it out and then it wouldn't start. It would crank, but not fire. After it sat for 10-15 minutes it started up like it normally does. Could the engine temp sensor be causing both problems? Also, we had rain down pouring for a couple days right before this started and my jeep was sitting outside. Thanks in advance for the help.
November 6, 2012.

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