1991 Toyota 4Runner

My 1991 4Runner wants to “die” when it idles. It will idle regularly but then every 3-5 seconds the RPMs will drop and then return, drop then return, so on and so on. I haven’t noticed any other issues, it seems to only be when idling that the problem occurs.

check the Idle air control

For the 2.4 l4 4 engine

Mass air flow sensor
For the 3.0 V6 engine