Then it's definitely not the car needing to relearn the idle. What's the next potential thing it could be?

 

Bad spark plugs, ign wires, etc.

 

Wouldn't such things trigger the Check Engine light to illuminate?

 

Since your car is drive by wire and it doesnt have an IAC valve I would agree with toyomoho the next steps to check are plugs, wires & coils.

If your car came equipped with platinum plugs they are at the peak of their life at 60K and will now start to degrade. Even if they are double platinum or iridium which should last longer it doesnt mean you couldnt have one that is degrading.

Does your car idle fine at a cold start and the idle is shaky once warmed up - or all the time?

A coil could be degrading as well? You should be able to remove the connector and perform an ohm measurement to see if it is in spec or not.
Of course there are cold & hot measurements to verify.

Same goes for the wires - heat can increase the resistance in them, perhaps one area of your engine bay is a bit hotter than others and over time has caused a little
drop in performance on those ignition parts in that location.

I doubt a CEL would be deployed in this situation of ignition parts falling out of spec ever so slightly.

 

Thanks for this detailed response. It idles fine upon starting and then rougher once the engine is warmed up.

Does this lead you to think I should test something specific first?

 

I would put new plugs in to start. I personally dont like to leave plugs in longer than 60K because I have had issues in the past
removing some that have been in longer. While youre changing the plugs I would also check all the COLD coil pack resistance values just to verify those
since you have to pull them to get to the spark plugs.

If the plugs dont help then I would measure the coils HOT resistance. More likely a out of spec reading here vs. COLD if you say the rough idle occurs after the
engine is warmed up.

 

I replaced the spark plugs with the same Denso plugs Toyota recommends. I gapped them according to the specs in the Camry's owner's manual. The rough idle (felt especially in the driver's seat) persists.

I didn't check the resistance values because I don't have a multimeter, but I can source one. What are normal hot and cold readings, so I have something to compare my readings to?

 

my camry doesnt have coil packs so I really dont know. try an internet search and see what you can find or buy a camry repair manual for your year and im sure the hot & cold resistance values would be in it

 

Did u ever find a fix? I’m having the same problem. Replaced all spark plugs and ignition coils. I’m honestly ready to set the car on fire now

 

Nope. Still an issue. I tried replacing the spark plugs, cleaning my washable engine air filter, cleaning the mass airflow sensor, amd using Shell V-Power for several thousand miles.

Please update this thread if you figure it out! I am also not enjoying this car because of this.