Good morning,



I have a 2013 Mazda BT-50 with a 3.2L engine/automatic transmission. I have noticed that the RPM surges or fluctuates when shifting from 3rd to 4th gear, along with a slight hesitation during the gear change. What could be causing this issue?

 

The first thing is to scan your ECU and look for current DTC and permanent DTC, then check your I/M monitors.
YOU WILL FIND DTC(S)
Even if your check engine light is not been activated does not mean their are no ECU control issues.
dirty or failing item to name a few can cause you issue:
To only name a few of the most common......

MAP sensor dirty or failing
MAS sensor dirty or failing
air filter
oil wet intake
IAP sensor dirty or failing
Throttle body (or carburetor if applicable) dirty or failing

You just need to gather more information

 

Welcome to the forum

 

ould any of these faults cause RPM surges or fluctuations when shifting from 3rd to 4th gear, along with a slightly hard gear shift?

ould any of these faults cause RPM surges or fluctuations when shifting from 3rd to 4th gear, along with a slightly hard gear shift?

ould any of these faults cause RPM surges or fluctuations when shifting from 3rd to 4th gear, along with a slightly hard gear shift?

ould any of these faults cause RPM surges or fluctuations when shifting from 3rd to 4th gear, along with a slightly hard gear shift?

ould any of these faults cause RPM surges or fluctuations when shifting from 3rd to 4th gear, along with a slightly hard gear shift?

ould any of these faults cause RPM surges or fluctuations when shifting from 3rd to 4th gear, along with a slightly hard gear shift?

 

Wow! You have may have a few concerns to resolve? But then see below first.
I would suggest you as a DIY re-set/clear the DTC all of them. Then wait overnight before driving the Mazda. The next day taking your scan tool with you as soon as the check engine light appears go retrieve and all DTC. You may have a few causes and effect by not checking soon enough for DTCs/