I have a 97’ Toyota 4runner with a 3.4 ltr. v6, 4x4, automatic. Whenever i have come to a stoplight with the truck in drive, there is a strange rumbling idle until i hit the gas to go. At first I thought maybe the motor mounts were worn, but upon further inspection, they look fine. It hasn’t been a problem until last week when it got worse. It got so bad the motor stalled twice. It starts right back up and no warning lights come on. I have changed every filter including PCV valve and trans. filter, plugs and wires trying to remedy the problem, and nothing has made any effect. the battery and alternator both test good as well. Any suggestions?