Yaris rough/low idle

[AngryPixies]

Hello wonderful people of the Internet! Hope y'all are doing well.

I recently bought a very nice 2009 hatchback Yaris as my first car. It has 115 000 km and is equipped with the 1.5 liter engine paired with the 5-speed manual transmission. The car has been fantastic except for the fact that the idle seems to be very low at around 500 rpm and it almost seems like it wants to stall but it never does. The idle only drops down this low only after the engine gets to operating temperature and it feels like the car is going to rattle itself to pieces. Also, the idle sometimes jumps to 750 rpm for a few seconds then drops down again to 500 rpm.

I have replaced the air filter, spark plugs, alternator (bearing was gone), cleaned the trotter body and the MAF sensor.

Has anyone of you guys experienced this problem before? If so, how did you fix it?

 

[TonyHSD]

Hi and welcome. 
Rough idle can be as a result of air fuel mixture. 
You did most important jobs but still having some trouble next you will need to check if your engine has a cable operated throttle body or electronic. If it’s cable operated then should have idle control valve fitted ( ICV) on it , a black plastic actuator motor. If yes then you need to take this one out, clean and inspect, find online how to measure it to see if properly work and if not within the specs replace with new. If oem or aftermarket are too expensive you can search in aliexpres , they offer parts like that that are good quality on reasonable prices. , but you need to have the correct oem numbers and compare pictures and yours match exactly.