Hello everyone! I’ve just recently got into the evo world. Picked up my first 8 with FBO. Unfortunately it’s been a pain… After driving the car for about 20 minutes or so it comes to a point where it’ll idle weird and then when I start driving again I’ll come to a stop or put it in neutral to coast and the car will drop rpms and die. Itll crank back up and will stay on if I’m giving it gas and drives fine. I’ve replaced map censor, cam censor and installed a new battery. Next is
the iacv. My plan is to clean out the throttle body when I replace it, and check for boost leaks. This is my first real car so I appreciate any help i can get, thanks!

 

Its 150% the IAC valve

Super common. Super annoying. Super easy fix!

 

I second the IAC as a possible issue. There is a test for the IAC you can run to see if it is working as well.
Checking for vacuum leaks is also a good idea as I have had these cause similar issues in the past.

 

I sure hope that’s the problem, I did buy an aftermarket evo 9 one… some have told me they’ve gotten lucky, I’ll try a few and if not I’ll just get an oem one. Going to change it when it gets here probably Monday/tuesday. I’ll be back with an update then, thanks!

 

IAC has to be set to a voltage or % open to work properly. Search and I bet you will find a tutorial.

Mitsuatb

 

any smell of fuel when its acting up?

 

maybe stating the obvious... but does it have a VTA bov ? it messes up the maf airflow calc's and caused the engine to stall...

put a stock 9 bov on it and it will not have the issue anymore

 

no not that I can remember

 

It has a tail bov

 

that's the problem...

 

Update!!! I cleaned out the TB and put a new iacv in and it does start but will be sluggish in the beginning, I do have to just be slightly on the throttle so it stays at 1k and then once it warms up it’ll bounce from 1k to 1.4k until it’s completely warm which then it’ll go back to 1k and idle fine and I am able to drive it without any problems so far. Could the iacv still be bad?

 

Yea, this sounds like a bad IAC or the tune isn't quite right for it.

 

Is the car tuned? My tuned car did the exact same thing… updated the tune and it fixed it.