Hey SKYLARR. JADE,
No problem. I understand you want to avoid going to the dealer if possible.
Vacuum leaks can for sure cause the issue you are having, if you have a leak it will cause unmetered air to get into the intake which affects the idle. When the engine heats up expansion can cause the leak to seal and your idle can then improve.
Checking the plausibility of the temperature sensor readings if you can access a scanner with live data would also be a good idea. With the vehicle cold, ignition on but engine not running you can compare the coolant temp, ambient temp, intake air temperature etc. This will give you a good idea if any are giving an implausible reading.
Throttle body cleaning is a good idea as contamination around the throttle plate can cause a reduction in idle air flow. It can also cause the throttle to stick and not reach the desired position that the ECM is trying to achieve.
One last thing that might be worth trying is a battery reset. If you remove the battery cables from the battery and connect the positive and negative cables together (normally for around thirty minutes) it discharges the capacitors that keep the memory in the ECM stored if the battery is disconnected. You must have the battery cables clear of the battery terminals during this process, to be safe remove the battery.
This is know as a battery reset, hard reset or capacitor discharge.
Please if you are not comfortable with this process get a shop to do it. You can cause damage if you short the cables together whilst still in contact with the battery terminals.
This will reset learned values in the ECM, if this does improve the situation for a while it does point to potentially programming being a cure to this issue.
Any further questions please do not hesitate to ask.
Tuesday, April 2nd, 2019 AT 9:16 AM