My Corolla 2014 has this issue where revs fluctuate quite a bit at idle, sometimes dropping to 4-500 revolutions and going back up. I changed the MAF sensor, cleaned the throttle body, replaced the air filter, replaced spark plugs, and it still does it. Also, there’s no CEL or codes. I took it to my mechanic and they couldn’t find anything wrong with it.
What could it be?
It’s got 98.5k miles. Car has been serviced regularly.
I found this answer on stack exchange for an 09 - “Resolved (so far :) - last week replaced the timing chain tensioner (Toyota OEM #1354037030). The noise at low load is now gone and the RPM needle remains steady at idle.”
https://mechanics.stackexchange.com/questions/67722/corolla-idle-fluctuation-and-noise
That seems like a plausible solution. I’ll definitely look into it. Appreciate it!