89 buick century idling ruff when started, and fan comes on right away even though car is cool, but drive ok ones you get going? Ive got a code 22/ 42 Thanks so much

A cheap cooling sensor might not start the fan. Make sure the one you or your mechanic bought is a quality product.

if you mean the rad cooling fan motor then it may not be any good and needs replacing as this can cause a car to run hot at idle and drop when driven with the a/c on with the extra load on the cooling system if there is 2 cooling fans on the rad.one works when the a/c is on or if the coolant gets too hot, you could also have a poor radiator that needs replacing(flow restricting)

BOTH!... when you find out WHY the fan is not operating, let us know... OK?

cam shaft sensor

The fan switch is under the alternator. The turn on temp is 238. Have you checked power at the relay? If you ground the wire at the the temp switch does the fan come on?

Check the fuel filter, it might be clogged.

could be the O2 sensors

High idle is computer controlled to try to get fan moving enough air to cool it down (so that part is normal) check that electric fan comes on and check clutch on mechanical fan if you have one. If all OK, radiator may be partially internally plugged or may have leaves stuck between it and a/c condenser.

change your thermostat it may not be opening all the way

I had just wen through this with mine does it sometimes idle high  also look out for the cooling fan coming on and staying on even when just turning on the key cold if you experience any of these check the trouble codes for a i think 26 quad driver circut if you get anything that comes back as quad driver circut you must replace the engine control module. cheeper than replacing the car  mine is perfict now