I have a 1994 Grand Cherokee w/4.0L, auto, ac, power windows, power locks and 4 wheel drive. I have a temperature dependent cruise control problem, as the temp. outside warms the cruise control quits working, I'm in Kansas. This event occurs roughly 50 miles after constant driving. Along with this, the vehicle will lurch forward as the cruise accelerates and deaccelerates on its own, before the 50 miles. Once the cruise has quit working the speedometer and the tach cease to work. All other gauges on the dash continue to work. This only happens during the warm months, late spring thru early fall.