Hesitation problems gone in cold weather?

2012 Honda Civic LX, 180k miles.

First, can a transmission mount affect acceleration performance? I've been having hesitation issues (lack of acceleration power) in my Civic. The problem goes away almost completely in cold weather (anything below 35 degrees F). However in warm weather, my car struggles to accelerate quickly and it sounds kind of like it's growling.

I do believe I have a bad transmission mount due to a vibrating/rough idle that goes away whenever I shift to N or R. So I will get that replaced, but I'm not sure this can cause hesitation?

Does this sound like a dirty TB?

Fuel trims are normal.

Sounds like a vacuum leak. Don't know what a fuel trim is…

Maybe. A bad mount would allow your engine to move a lot, and the torsion could widen holes in your intake which means too much air that is unaccounted for, also dirty. So check around that area. Wiggle your intake around and listen for changes in your idle, buy a new rubber intake if its compromised. Also check your air filter. Summer brings a lot of pollen, bugs, and other particulates.

Clean the MAF sensor.

A bad trans mount would not affect acceleration… More likely you have an issue with temperature related sensor or devices on the engine since the problem occurs moreso with a warm engine… Or ignition system issues.

The problem could be due to EGR issues which the PCM only opens up when engine is warmed up… Possibly a clogged passage, bad EGR, vacuum leak, etc.causing the EGR to malfunction and cause power loss.

Or a faulty coolant temp sensor… CTS… Or Air Temp sensor… IAT, etc. Can cause issues… Any sensor that senses coolant or air temperature and gives a faulty reading to the computer can affect engine operation… And may not trip a trouble code if the sensor value is still within parameters… Just wrong for actual conditions. If a temp sensor tells the computer via voltage readings that the engine coolant or air temp is cold when it is actually warmed up, then the computer will set improper fuel trims for actual operating conditions… Too rich. Which is why the car may run better when cold since the faulty CTS or IAT sensor values would then perhaps agree with actual conditions. Most often a faulty CTS sensor but further testing may be needed.

Some temperature-related issues can also be caused by defective ignition parts such as coils or modules which can work fine or better when cold but have problems when hot or warmed up due to high internal resistance… Leading to weak spark, stalling, poor power, etc… Ignition system defects may also not trip a trouble code/CEL light if they are not part of the closed loop computer system.further testing is needed.

A shop can test internal resistance values of ignition modules or coils when cold or hot and see if they are too high or improper. Or check for weak spark on a hot/warmed up engine. Use a scan tool to test for temp sensor values /readings and compare to actual conditions… Or voltage test the sensor values and compare in repair manual charts.

With such high miles, it's also a good idea to clean the IAC, MAF and TB of any soot buildup which can affect idle speed or engine operation… And check for any vacuum or air intake leaks. Run some Seafoam or Techron additive in the fuel tank to clean injectors.