2008 Kia Sorento with a V6. Runs rough when cold, after gets to operating temp runs good. Though it would have been injectors but they checked out fine 15 ohms on average give or take 1 ohm. What could it be?
Injectors checks are more than just just checking the resistance. Do they leak? Do they make a good spray pattern? Why did you thing checking resistance would identify a rough running problem?
How many miles on this car? I’d guess it is a coolant temp sensor problem as a first try.
Check engine light on?
A vacuum leak which partially seals as the engine warms up can produce the exact symptoms you have
If the problem isn’t severe enough, it won’t necessarily generate a fault code