I've scoured through countless high idle posts and tried numerous fixes/suggestions but no luck.


Evo 9 - Idling around 2 to 2.5k rpm, mostly.

This issue seems to have started after a 4th gear pull. My initial thought, of course, was vacuum line blew off. I've ran many BLTs and patched random leaks here and there and the only one left is a very small leak on the gasket on the bottom of the turbo. The BISS screw also seems to have a very small leak and I replaced the Oring but it still seems to be leaking. No other vacuum/boost leaks to be found.

Most of the time, from a cold start the idle will be fine until I warm it up and do pull.. then it goes right to 2k-ish. But other times it will be high idle right from the cold start. It seems to have no rhyme or reason. Also, it is not a bouncy idle and will just hold at high rpm.


I've replaced the IAC with a new unit from STM. No change.

I did not replace but I've tested the TPS with a meter and the voltage values seem dead on where they should be. Could the TPS still be faulty if the voltages values are accurate? I assume if the steps in the sensor are fried - how could I test for this?

The throttle cable has plenty of slack.

Took TB off and the plate has no sticky spots. Also cleaned the TB. Shaft seals don't appear to be leaking.

EGR has been deleted a while ago.

Is there any chance the BISS screw could have backed out for whatever reason? It's currently about 7 full turns out from fully screwed in.


Happy to provide more info if needed.

Any input is greatly appreciated.

 

I have this issue but I havent found the time to look into it. its not a big issue for me since it helps in autox lol.
does the idle rpm go down to your desired idle rpm when you turn the AC on? if so that means the issue is somewhere in our SD tunes

 

It does not go down to the desired rpm but does lower a little.
The car was tuned by Raif about 4-5 months ago and the issue only started recently - nothing was changed on the car since the tune.

 

maybe you can experiment blocking off your pcv & brake booster hose (both have check valves)and see if affects the idle rpm.
mine does go down to desired idle rpm with AC on. my random 2krpm issue seem to have started when I updated the idle stepper table and increased my idle rpm a little. i havent found the time to get back to it since I use AC all the time

 

Thanks, I'll give that a shot.

Any chance the TPS could still be faulty even if voltage test seemed fine?
Also, what are the odds the BISS screw can back itself out?

 

bump

 

I doubt it but it has an o-ring that could go bad

 

The o-ring was leaking and I replaced it with one I was able to source from advanced auto (it was a 1/4" ID x 3/8" OD x 1/16 W) but it seems it is still leaking. The only info regarding o-ring size I was able to find online was the DSM forums. Is the Evo o-ring different? Seemed to fit well, don't know why it's still leaking.

I went out today and was playing around with random bits and decided to hit my coil boots with electric cleaner.. seems to idle perfect now.
Such a strange thing but so far it seems to be fixed..

 

i really doubt a tiny boost leak with cause a 1k+ rpm increase. you can replace the whole thing if you want https://www.ebay.com/itm/27549808327...Bk9SR9zwo7jBZA