Ok I've been having a idle problem for some time. Idle hunts when coasting in neautral and just in general the car at a stop idles around 1100 randomly chiilling at 800rpm or going to 1500rpm for a while. Fixed a couple vacuum leaks and don't think I have anymore. Still looking but besides that I know one of the issues could be the iacv. I bought a new one off a evo9 and am awaiting install but I know the biss(base idle set screw?) has an effect as well. The last owner of the car toyed with it so idk if he touched the screw so basically..

When I out in the new iacv what is the stock setting the for the BISS? Ie if I screw it in all the way than do a quarter or couple quarter turns.

Its a 03 evo8. Had the ecu looked at and was told everything looks normal.

Thanks for the help.

Trying to get my car running perfect. It's hard not spending the money on performance parts

 

Use evoscan. There is a set idle screw button which stops the IAC. Then set the biss to about 800. BTW, how was the ecu "looked at"?

 

Had a fellow evo owner look at it. I plan on getting the car flashed after I put on a turbo back anyways which I'm sure I can figure everything out than but I'm just trying to figure it out now "assuming" everything ecu is normal

 

Goin for a bump

 

As said above the only way to correctly set the base idle is with Evoscan or a MUT tool, as it involves parking the stepper then adjusting the BISS to get the correct airflow bypass for constant idle at around 850rpm.

 

What BOV are you using?

 

Stock Evo 9 bov on my Evo 8

Thanks grayw I'll look into it. Don't have the scanning tools so I'll look for some help on that

 

do we do this when the car is warmed up or cold???

 

sounds like your iac.

did the previous owner run meth? some meth users end up with burnt biss screws. but that shouldnt cause eratic idles.

for a basic setting, run the biss screw all the way down & turn it out 1 revolution. most oem tb's have their biss screwed in about 1.5 turns out from bottom.

 

Thanks that's what I was wondering.
I think the guy before was running meth because my intercoooler sprayer is gone and someone told me that's what some people use when switching

 

Just wanted to bring this one back real quick..

only ONE turn out? That seems low? I think I am at 3, and it still stalls rather easily.

 

ive read somewhere stock is around 3 1/2 out is what they are all at from factory.