My 4runner has developed this random issue. Everyonce in awhile when you start it the idle will start jumping from 800rpm to 2000 and then back over and over. If you shut it off and leave it a minute or two and start it again it'll be fine. I'm scratching my head because I can't figure it out. It's hard to make it do that and you never know when it will do it. All i can think of is possible there are some old vacuum lines that are leaking? Does anyone have any ideas?

 

I got in it this morning and it idled good for 20 seconds and then it started it's up and down idle from 1500 to 2000 and back. I put it in gear and it idled fine at 750 rpm. When i got to work and put it in park it idled at 1200 and slowly dropped to 900 where it stayed. i'm only having this problem when it's cold outside.

 

possibly the cold start injector is going up? That would be one thing to look into.

 

try adjusting the ide screw?