My evo ix has an issue with dipping idle if I put it in neutral say cruising at, 3k rpms. Not using ac. It also does it in first gear say I'm in traffic on and off the clutch in first rpms drop passed desired 1100 rpm down to 400 and sometimes not always will stay idling at 400 until I give it throttle. Car has 24k miles. I've searched and searched found no solutions. Pulled Iac tested resistance values.. All in spec. Teeth are intact, and hear it moving with ignition on. So what else could it be?

 

Vacuum leak

 

sorry should have mentioned had a boost leak test at 30 psi and checked everything. No leaks anywhere.

 

Bumpski

 

I'm also having this problem on my 8. Happens randomly though, I can't make it happen on command. Some days it does it some days it doesn't, weather doesn't seem to have any affect. Still have yet to check the IAC though...

 

mod list? tuned? maf or sd?.....etc

 

im having the same problem but i dont think its as extreme as yours

 

It's an issue in the tuning. I hate to use the term it's normal but without getting a custom tune to fix the iacv tables or whatever it is not much you can do about it. Swapping to speed density seems to fix it in some cases but other than that suggestion no confirmed fixes.

 

Well this would make sense, im assuming everyone here has larger injectors?
I have the same issue when I enter boost, and suddenly let off and coast.

Ill have to research the IAC tables to tune that out. Or does nayone know how to tune it out?

Currently running 1000c PTE's, im pretty sure its not the bolt ons never had this issue until bigger injectors came

 

Mine does it on stock injectors, idk exactly where it is ( I'm not to computer savvy) I just kno that's wut db and English racing has pointed to in past threads on this issue.

 

The coils on the IACV can go bad (check them with a resistor) or the tip can melt if you have the plastic IACV (the IX should be metal) and use meth.

Generally there is tuning you can do to help. I haven't been tuning the CT9A for a couple of years, but there was no definite tuning solution last time I was looking at it.

If you BOV is VTA it will definitely cause this (unmetered air escaping = rich condition).

You may also have a post throttle body leak or be leaking at the butterfly valve seals. A boost leak test may not show these conditions.

 

Sorry for not saying all of this initially. I have unknown cams, tbe, head studs, Springs from previous owner. Didn't have this issue. Got a custom intake, fic 1050cc injectors, Walbro 255, grimmspeed boost solenoid, new tb seals and gasket, and a tune. This idle dip issue started the day after the tune. I'm running stock ix crushed metal diverter valve recirculation. Running stock maf no SD.

 

Bumpington

 

Bump

 

have the same issue with my car. only when running the evo 9 bov, ran a forge no idle issues :/