I have a IX RS with the following mods:
full exhaust, no cat, map O2 dump/DP
ams LICP
custom fabbed maf pipe, perrin filter.

stock boost, stock tune.

now that it has turned cold, the car runs like ****, i get misfire codes if i am not super gentle with it. it hiccups when the turbo begins to spool, and at around 12 psi, it feels like the car hits some sort of rev limiter and wont rev out under full throttle. ive changed spark plugs a few times, with no change. i KNOW it needs a tune, so i dont need that lecture, but im wondering where do i start if i cant even make full throttle log runs.

or do you guys think something else might be wrong? when it was warm out, the car would run to redline @ full boost no problem.

 

Just started happening when it got cold?

 

You might try getting a starter map from one of your peeps with similar mods whose EVO is running a-OK. That will give you a good starting point to dial it in.

 

yeah, pretty much. it started out that every once in a while at the top of 4th gear, the boost would creep up a little to about 24...and BANG everything would shut down for a second. when it was warm, the boost did not creep. the colder it gets, the worse it runs....however, now, it pretty much runs like **** all the time, under boost. ive checked for boost leaks...and cant find anything obvious. could my bov be bad...it flutters alot when i let off the gas in higher gears but at lower speeds...

im stumped here.

 

Are you sure this is not simply boost cut?

Try raising it a wee bit.

Actually, what boost level are you tuned for? If you are over boosting your tune in cold weather, just dial boost back a bit.

 

stock tune....stock boost.

 

I would put a wideband on cause with those mods the worst you could be doing is running rich. I would suspect a different issue not weather. Stock BOV?

 

He would be running "real LEAN".... thats whats probably causing misfires as well.

 

it does have stock BOV, and like i said...it flutters alot, off throttle. its warm today, but the car still runs bad. pops, misfires, and stumbles when the boost comes on, and if you hold it wide upen, when it gets to about 12 psi the boost guage needle just flutters, and the car has a steady sputter...like a rev limiter...it sucks.

 

Do you have a boost gauge? How do you know that your are still running the same as stock boost with the above mods?

I'd say there is a very good chance that the above mods are allowing the engine to breath much better and resulting in higher than stock boost levels, and, perhaps/likely running lean as well. Both are a big no-no without a proper tune.

 

My stock bov flutters at low boost. I would check the coils.

 

yes, i have a boost gauge. problem is...the car ran fine all summer with the above mods, and has slowly deteriorated. Not sure if the cold is a coincidence....but like i said....it runs like crap even on warm days now...so i dont know whats wrong with it. im running bpr8es plugs gapped at about .022. before that i used br7es plugs gapped the same...before that the stock iridium plugs. the car started to run poorly on the stock plugs...so i changed them...

what do i do to check the coils? the car also has an HKS twin power box on it....but it seems to be working properly...i dont know how to check that either. thanks for all the help brainstorming guys.

 

Might be hitting boost cut since your still on the stock tune with those mods that would increase airflow...

Do you have any signs of damaged to your BOV?(cracks, etc)

Also, do you have a Tactirx Cable?

 

Try eliminating as much as possible.

Unplug the boost solenoid so it is only running on the waste gate.

Remove the HKS ignition box; you don't need it anyway.

You could even disconect the waste gate to see if it runs OK n/a.

 

i have checked everything today. cant find a boost leak. checked every vacuum hose and ic pipe...everything. compression test, everything. ugg. i dont know what to do next to troubleshoot this problem.