To understand rough running after spark-plug replacement, compare it under normal, safe conditions: cold versus warm, idle versus steady speed, and light versus higher load. Record which plugs were changed and whether the issue began immediately afterward. Change one condition at a time so the result stays useful.
Do not create a risky test just to reproduce it. Recheck the correct plug type, connector seating, and any parts moved during the job.
Quick educational note
For information, not a diagnosis or repair instruction. Vehicle-specific checks are still required. Consult the manufacturer's guidance and a qualified technician.
How to use this information
This article explains general principles and does not establish what is wrong with your vehicle. Read the content limitations.