'96 Corolla RPM idle issue :(

RPMs fluctuate from very high to very low without me doing anything.
It doesn’t do it all the time, so far its happened 4-5 times in the past 3 days. I first noticed it when driving, i took my foot off the gas to break and it started doing it and once i hit the gas it stopped. It seams to be getting worse because today i put it in park and when it should have jumped into idle it started and even when i hit the gas it didn’t stop.
Like i said the RPMs fluctuate from vary high to very low in a few seconds regular intervals.
Any ideas?

I would start with the Idle Air Control Valve. Is this happening while the car is in drive and coasting? or just when stopped. (Also check the vacuum hoses coming off of the IAC for leaks or a disconnected line)

I have a similar problem w/my early 90’s Corolla. Here’s a link from when I posted about this topic.


So far I’ve eliminated the power steering vacuum switch, the canister purge valve, and the idle-up vacuum switch. Next up is to look for vacuum leaks in the brake booster and the egr. If none of those, I’ll try cleaning the throttle plate/bore and see if I can clean/inspect the idle air control valve without removing the whole throttle gadget that bolts to the intake manifold.

My symptoms are different than yours. Mine, one day the warm idle was about 250 rpm higher than it was before. For no apparent reason. Based on your symptoms, I my first guess is your throttle valve is sticking and needs a cleaning.