A few times the weather is cold and the revs of the engine not go up to heat the car other time they stay constant at 1000 must I change a sensor?

thanks

I think you are asking about 'fast idle'? While I am not certain about your problem, some of the comments in this thread may give you some ideas.

In general, since the idle speed is set by the ECU, any of the temperature sensor, the lambda sensor or the thermostat being out of specification, the throttle body being dirty, air leaks after the throttle body, or the throttle body needing resetting, could lead to issues.

OK thanks I have a problem with throttle.I will solve first this one.Second time I think I will change throttle bodying is that Normal about every 80.000 I am very disappointed.

If it's a throttle body problem, there are already instructions on how to clean it. After that, leave the battery disconnected overnight and it should be fine.

The only other gotcha I know relating to resetting the throttle body is to make sure the throttle cable isn't too tight. On our last Felicia I'd set it according to the guidance in the Haynes manual but even after leaving the battery disconnected overnight I was finding the revs were falling slightly too slowly when I took my foot off the accelerator pedal. It turned out the cable adjustment needed a little more slack and then after the throttle body was reset again all was well.