Hondata

Hello,

i am having problem with fast idle. Car drives just fine but i am unable to hold steady rpm in 2-3k rpm range while in neutral.
Because of this issue with fast idle i cannot legally pass emissions test so i want to fix it.
Car was tuned by Vit years ago, so my calibration is password protected.

my setup is:
k20/24 forged frank
RDX 410 injectors
RRC intake manifold
J35 Throttle body
Hybrid Racing CAI
Tegiwa 4-2-1 exhaust manifold
stock exhaust with race cat
4.7 final drive

i am attaching datalog from fast idling attempt, maybe somebody has an idea what could be the problem, bad tune or maybe some hardware failure.
I have also noticed that my short term fuel trims are around -15% while car is cold.

Thanks,
Trulex

Did the issue start recently, or has it been a problem since being tuned years ago?

Atleast 3-4 years, maybe even since tuning bit I didnt notice it right away. Not like i am trying to hold higher revs in neutral on regular basis.
Btw. when car is cold it can hold steady rpm in neutral, problem with bouncing rpms starts when car gets warm.
I tried swapping different intakes (stock, tegiwa, HR), exhaust (martelius, stock with and without race cat), cleaned TB, changed TB gasket..
Even tried with different AFM and ECT sensor because my HDS was sometime showing weird temp readings (ECT1 -40 and ECT2 over 200 celsius). Hondata shows normal temps so it was probably problem with HDS.

Only things i havent tried yet are replacing throttle body and o2 sensor.

Yeah your car is for sure speed density tuned, so changing the MAF and what not wouldn't yield any tangible results as it's basically just a temp sensor in you tune. Your ECTs are in Fahrenheit, at 200 c you would have some major issues.

If you want to run a test, I can send you a basefile to test your neutral rev issue and see if it's fixed. If it's fixed, then I would say it's most likely a tune issue. At that point you would need to decide if you want to retune it, or build a new map for emissions and use Vit's for everyday driving. The file I would send you would be a simple basemap just to test the neutral rev issue, to drive on it would take some tuning based on your setup.

Do you have any datalogs from driving and some wide open throttle driving? I am curious if you are tuned on a race calibration or not.

thanks for your input EFICU, looks like i managed to accidentally find the workaround over the weekend.
It is somehow AC related, once i turn AC off and then back on it starts to rev normally after few seconds.
I am usually running with AC on auto. Not sure what the root cause of such behavior could be, but car is otherwise behaving perfectly so i am not gonna bother with this annoyance anymore.