So, I've been having this issue for quite a while, and now it's getting pretty bad.
Here is the description:
When I'm driving in heavy traffic (stop and go), my engine seems to overheat, but the temp gauge stays in the middle (I assume the overheating is not critical for it to go too far up). With overheating my idle goes up, sometimes reaching over 3k RPM. This is never an issue in the winter. If I turn on my A/C right when I start my car the idle will be normal, even if I'm driving 10 miles in heavy traffic.

A mechanic replaced idle control unit in this car, this didn't help.
I cleaned the EGR sensor, no difference.
I do have Check Engine light on, but the error is telling me there is an issue with exhaust evap circuit, so it wouldn't effect my idle.

Now, when my A/C is running, radiator fans seem to run at the max, doing a good job. I noticed that if I turn off the A/C fans will shut down. They do turn on in a few minutes when the car is on normal idle, but it seems to me the fans are running at a slower speed.

I'm thinking of replacing a fan control unit, hoping that the temperature sensor in the unit has gone bad, or that the unit is not changing the speed of the fan.
Does anyone have any suggestions as to what the issue could be? Should I replace the fan control unit? I don't think I have issues with coolant temperature sensor because I don't have errors for it.

Any suggestions?

Thank you!

 

Fix the check engine light problem. Regardless of what you "think" it might be telling you. CEL cause the car to go into limp mode often. Can cause a bunch of other driveability issues.

 

"an issue with exhaust evap circuit, so it wouldn't effect my idle."
i wonder what you base that gem on...
Since the fans seem to work, i wouldnt dick around swapping parts.

How do you know your engine is overheating if temp gauge doesnt show it?

Mentioning winter, I have a suspicion that your car isnt tuned for the air density you live in. On an 06, probably sensor or computer.
And change to a summer weight oil.

 

and reset the ecu.
I have another suspicion that for whatever reason it expects the extra load of the a/c and is delivering more revs/fuel to compensate.
But i dont know **** about computers.

 

I did reset to ECU many times, last time was when I cleaned the EGR sensor. Light came off, but then after you start a car it comes on again. The error is P0446, evap system malfunction. The solenoid should be replaced, I'm thinking of replacing it myself once I find where it actually is.

 

The thing is - check engine light came on only recently, like a month ago. I had this issue for almost 2 years now. Mechanics I talked to don't think the evap solenoid can cause this problem, and I didn't find online any connection between my symptoms and the solenoid issue.

 

My fans work in a weird way.
Here is an example: my wife has exact same car, but 3 years older. In the summer, when she shuts off her car I can hear cooling fans working for another 10-20 seconds, cooling the engine. My car has exact same Fan Control Unit. It never does that.
Also, when I driver in heavy traffic I can feel that engine is very hot when I pop the hood - everything feels very hot inside. If I drive on a highway, the engine section never feels this hot when you open the hood.
Anothing thing, I just checked yesterday. I drive through traffic and bring my car to the condition of rough idle. I pop the hood and observe the fans - they would turn on and off, but work at a slow speed, even though engine feels hot and idles on 2k RMP. I turn on A/C and my fans start running at the max speed, noticeably faster. After about 2 minutes my car's idle is coming down to appropriate level. I shut off A/C and while engine fairly chilled the idle is below 1K RPM.

I also had a suggestion somewhere that my thermostat could be stuck half-way open, because of that there is a limited flow of coolant between the radiator and the engine. Because they are very cheap I'm thinking of replacing my thermostat just to see if it fixes the problem.

Going back to Fan Control Unit, I just wanted to mention that I read that these modules from around these years are not very resistant to extreme temperature swings. For the first 6 years of driving this car was in Minnesota. In that state temperature swing can be from 60 degrees F to 0F in less than 7 days. My problems started showing up after I moved from MN to Chicago (I know winters are still cold here, but they are much milder here).

 

i don't mean "clearing the code" i mean kicking the thing in the ***. disconnect the power overnight so it forgets what it knows and has to learn again.

so it seems you've answered your own questions, really...