najo

Hi all. I have an 2005 Evo 8 that has had constant idle issues since the day I bought it. I've taken it to multiple shops who have tuned it and tried various things to fix it and none have resolved the issue. There seems to be an intermittent problem with the IAC. The car will start and drive fine for a while and then the idle will randomly start acting up, bouncing everywhere and eventually most of the time the car will stall out when I come to a stop. I have to feather the gas pedal when I'm going slow to keep it running.

I have no clue what causes the idle to start behaving erratically. Swapping IAC's has not worked. As far as I know, there are no boost leaks as I am currently making 560 hp at 28 lbs of boost and it pulls great. Below are some of my mods. The car is currently running on pump gas. Has anyone else experienced similar issues running an AEM V2?

KC 272 cams
Walbro 450
AEM Infinity V2
FIC 1650 Injectors
AEM FPR

CurseDSM

iTrader: (3)

Swapping the iac not working that would mean the tune needs to be adjusted. What is your afr when it idles and when it acts up. Maybe it is doing it due to possible in between cells due to maybe rpm or something. I would log and see what it is doing log afr and see if it can be tuned out.

najo

I just had it tuned. Doesnt seem to be tune related. AFRs are around 15 at idle.

evo.matt

iTrader: (3)

I'm going to guess you're on speed density and egr as been deleted? If so then that throws away one of my ideas

najo

Yes im running on speed density with an EGR delete.

CurseDSM

iTrader: (3)

You must have been thinking boost leak like I was weren't you? It doesn't matter if it was just tuned or not. I have had problems with tunes after my car was tuned for one reason or another. Does your afr change when it decides to get all screwey? Does it go rich and then back to lean then back to target afr? Tell us more about what the car does and what changes.

najo

AFR's are all over the place. It goes from rich to lean, etc. as it's trying to reach the target AFR. Sometimes it does it at start up both when the car is cold or at operating temperature and other times it will start fine. It's set to idle a bit higher on colder temps then come down to target AFR and RPM as it warms up and it'll do that. After driving it for a bit even if it starts okay, it's hit or miss when it starts acting up. I've driven it home two hours without it acting up and as soon as I got home and turned it off and back on again, the idle started acting up. Sometimes turning the car off and back on again fixes it, but most the time it'll be temporary and continue to do it again.

4b11slayer

Sorry to thread jack sir.
But what would this indicate?

My e85 fp red and gsc s2 does this.

Sweeps rich to lean alot.

Also when coming to stop idle drops low and afr goes to 17

CurseDSM

iTrader: (3)

It indicates maybe a cell in your idle is higher then the other. Why I asked about how it does it. One of my other tunes the idle was tuned for target afr and with the cams i had it would actually hit a different cell at idle so it would do something similar to what the op was saying. So in my case it would go 14.7 out to 17 back to 13 and then correct itself. Well after changing a few things tuner had noticed something wasn't right with the tune. So it was just personal experience and I thought i would through it out there to see if it was doing the same thing.

CurseDSM

iTrader: (3)

OP how old is your map sensor or do you know. Wondering if the map sensor maybe wackey causing it to do it inconstantly

4b11slayer

In high octane fuel map?

mines5

What i have come across is that most of the idle issues are related to hidden vacuum leaks, wrong vacuum routing, faulty IACV , tps gone whack. Get all these checked n fixed and you will be good to go.

Can you share your map ?

najo

I'm not sure how old the MAP is. My tuner said it was intermittent the first time I took it to him and he thought it was wiring so he replaced the harness and heat shrinked it.

CurseDSM

iTrader: (3)

He is running speed density vac leaks wont matter.

CurseDSM

iTrader: (3)

Well for those running stock ecu yes, I run a Haltech and that is what we found it was just bouncing off each other. Once we smoothed out the cells it went away Idk crazy car I guess.