If its only over heating when stopped I'd check your fan clutch. Inspect it for signs of wetness (oil leaks), physically grab it and feel for play, and spin the fan by hand ( it should have some resistance and not free spin).

 

Yes, +1

Rising temp gauge while stopped is classic sign of Failing Fan Clutch
Can also be water pump impeller issue but much less likely


The fan is only there to provide air flow thru the radiator in stop and go traffic or when vehicle is not moving.

 

 

Also the sign of a cracked head/bad head gasket. Keep an eye on your coolant level.

 

When COLD the fan clutch will be tight
Thats the noise you should hear when you start a cold engine, a louder rush of air from locked up fan clutch, then that noise goes away after a few seconds when the oil inside the fan clutch gets warm from spinning.
Then the fan should spin easily, so start engine, let it run for 30 seconds then shut it off, fan should spin easily now.

Then drive it for 15-20 minutes, shut it off and fan should be tighter, you can move it but not spin it, if not then replace fan clutch.


The fan clutch works from RADIATOR HEAT, not engine heat, on the front of fan clutch is a bi-metal spring, as it heats up from hot coolant circulation in the radiator it closes off a valve in the clutch, which causes fan to spin closer to engine RPMs, it never fully locks, just gets tighter and tighter as radiator temp gets hotter.

When driving, the engine is under a Load, so gets hotter, when you stop, the heat from that Load is still there for a minute or two, but lower RPMs(idle) circulates less coolant, and lower speed causes less air flow thru radiator to dissipate that heat, so you have more heat and less cooling.
That is really the only reason there is a fan for cooling radiator, low speeds and when stopped is when the fan is needed, so heating up at idle would be a problem with.......................the fan
This is also why electric fans are a popular choice, mechanical fan uses horsepower all the time, but only needed maybe 5% of the time

There are a few of reasons an engine will get hotter at idle:
1. Fan clutch failing is at the top of the list and most common reason

2. If center of radiator is clogged up, fan clutch never get hot enough so never engages fully

3. General blockage causing low flow thru radiator

4. Leafs and debris clogging up air flow thru radiator

5. If water pump impeller is eaten away by electrolysis, it can't circulate coolant fast enough at lower RPMs

6. A lean fuel mix at idle

7. Failing spark advance at idle