my jeep has 212000 miles and i work till midnight. it has been extremely cold lately as you know, and i live in arkansas. it has been getting down to 10 degrees the last few nights. i have been having problems the last few days actually..the check engine light came on tuesday night, and then the next night, after i started it up to go home and let it warm up for about 20 minutes, i tried to take off and i could not go faster than 10 mph...it was extremely hard to accelerate and i could barely punch the accelerator...i let it warm up again and tried driving it once again, and it was slow to accelerate at first, but finally it was easy to accelerate again. i have mostly water in my radiator and i am wondering if my motor is freezing up at night....i checked my oil and it has no signs of coolant in it. the transmission fluid is fine also. what is going on???