Hot weather idle problems...

[10fold]

So every summer for the past few years (ever since I bought the car actually) my idle jumps up to around 2k rpm after driving around for a bit. I know it's not the ISC, I tested it and it tested fine. I even brought it to my mechanic who put in a brand new one and it still jumps up after driving around for a bit. I've cleaned the throttle body, adjusted the clip all the way to the left so there's slack in the throttle cable and replaced the O-ring on my base idle set screw too but nothing seems to work. I really don't think it's your typical idle surge because there isn't any real surge, it's just a consistent high idle when it gets hot under the hood.

When I flick the gas pedal with my foot real quick the idle drops back down for a bit, I also pop the hood and hold the throttle plate wheel all the way closed and the rpm's drop down for a bit but both are only temporary as the idle climbs up again after I drive around. The only thing that really gives me a consistent idle in hot weather is if I drive around with the hood popped a little bit...but I really don't want to drive around with my hood popped all the time. Hopefully someone here can help me out because I'm stumped...thanks in advance guys.

 

[gofer]

Check for vacuum leaks, at idle your boost gauge should be around 18in/hg.

 

[10fold]

It sits around 16-17 at idle so I think I'm pretty good there. I did take off my throttle body for a more thorough cleaning and that seems to have done the trick. It was pretty gross in there

If anyone has an idle problem like this that isn't surge, I'd say definitely check the throttle cable first, then take the throttle body off and give it a good cleaning.