RPM dip, stalling on idle

[Cebal]

Hi. Got pretty annoying problem to deal with. Searched internet/google for a fix but nothing helped.



First of all I have a manual transmition, boosted BRZ with FBM turbo kit. The problem is that when im driving, comming to a stop sign I put it in neutral gear and my car's RPM goes really low like 400-500 RPM, feels like car is almost stalling. It stalls once for a while cause of that and im trying to find a solution. I think it's getting worse when the car is getting hot. No CEL at all. Battery is weak but the car starts fine every time without a problem. It feels like car runs just fine when on gear, it pulls etc. When I rev it to the limit and hold it for a sec or 2 it sounds like it backfire's. Could faulty o2 sensor cause misfires on all cylinders? I ran out of ideas to be honest and im looking for your help. I checked logs using EcuTek connect app and there was multiple cylinder misfires. AFR on idle is between 12-16.



List what I changed/checked already to fix it:
- changed spark plugs, new HKS M50-HL plugs
- changed coil packs, new Delicious Tuning OEM+ coils
- changed injectors, new ID 1050X (remotely tuned them)
- changed MAF, new OEM one
- changed Coolant temp sensor, new one
- changed throttle body and throttle body sensor
- clamped evap lines under the intake
- checked for vacuum leaks, all good
- installed boost gauge, its building boost just fine, 10 psi like it should
- all 3 bolts on injectors module are solid



I made a short log how it's running on idle and I captured the moment it's RPM hunting and dipping especially at the end of the log. It does it on idle after I press on acceleration pedal and RPMs go down. I dont know what my fuel pressure should be so im not sure if it's right. I assume fuel pump is fine since my car starts fine every time.
Look at the log, there's multiple misfire, wild AFR, RPM dip etc.


https://datazap.me/u/cebal/log-16118...og=0&data=3-19


Thanks in advance

[humfrz]

Originally Posted by Cebal

Hi. Got pretty annoying problem to deal with. Searched internet/google for a fix but nothing helped.

Thanks in advance

DAMD, Cebal, talk about throwing parts a problem -

How about checking the tune (or did I miss something?).

I'll ring up ol @steve99 for you, he may have a suggestion.

[Cebal]

Yeah, I know, I know Threw in few new parts but some of em needed to be changed anyway. It's just im so annoyed that I dont mind anymore.
Well the tune was spot on before, had zero issues. It just started all of a sudden but it wasn't so bad few weeks ago. Now I just dont feel like driving it before I fix the problem. It happened before on 550cc injectors, I swapped them out for 1050x, my tuner made a tune for them romotely but It didnt help. Im about to meet him but won't be that soon since his away for few weeks...

[tomm.brz]

your problem is that ecu is forcing the Fuel Injection PI ratio to 100% at idle

that usually happens normally after a cold start and last not long, before switching to 0% (so 100% DI)
the fact you have bigger injectors exacerbates this as the injection time is really short and injectors have difficult time with a so short opening time

therefore, fueling is atrocious as you can see from log
If you get to have only DI at idle as it is supposed to be, you will fix it probably
You can check it also by the value " injection mode d4-s"
when it is 1, it s like it thinks it is still in cold start mode, and uses only PI at idle
It must become 2 or 3 to be good

American tunes always have bugs like this with ecutek racerom, it's annoying a lot
I encountered this bug many times in US tunes
, and it seems ecutek don't really care about it so if you don't get to have it work correctly you can ask your tuner to force-upgrade you to Euro A02G rom that will fix any bug

[Cebal]

As long as you may be right Im still wondering how is that possible that on my earlier tune with 550cc all was fine, then one day after few pulls on my way back home it started to work like garbage. Also there is negative Short Term Fuel Trim. Its worth mentioning on the log you can see that fuel quantity is pretty stable but RPM is not.

Gonna check my o2 sensor since the idle AFR is not stable at all and will update if anything has changed after the weekend.

[tomm.brz]

it' s not the afr sensor

it's the thing I told you :P pretty sure
Did you get an update from your tuner lately?
he updated you to racerom 12.1
I faced same issue with B01C and RR12.1

You can fix it force upgrading to A01C
and if it keeps staying in injection mode 1, you need to go Euro tune like A01G or A02G

or you can ask your tuner to downgrade the racerom version, maybe RR11 doesn' t show this bug

[Cebal]

Nope, still no update from my tuner but thanks, will let you know soon!

[tomm.brz]

No, i mean
when did you flash this last revision? you said you changed injectors and then problems started?

[Cebal]

Nah, I had this problem started all of a sudden with 550cc injectors so I swapped them out to ID 1050X, got my fuel map remotely flashed to work and the issue is still there.

[tomm.brz]

well, the same problem of yours I faced it with the more recent Racerom patch
So something in your tune got "broke" (bugged, since i 'm sure and saw multiple times that there are lots of bugs in US tunes with racerom)

Do you have a log with the previous injectors where you had the sluggish behaviour? I bet "injection mode d4-s" is steady at 1 at idle


you are in europe, why the hell do you have a bugged US tune in your car?
you'll need A02G or F10G for your car to have it run good with ecutek RR12.1
Even if it s an import, you ll need to change tune

You won't fix it in any other way keeping it like that, then you can also not believe me

[Cebal]

Yes, im in Europe and yes it's an import car but how do you know it's a US tune? Well, I have zero idea about tunes or tuning so I can't really tell which RR I have tbh. Unfortunatelly I dont have my previous tune anymore :/
Thanks for your help, Im gonna let my tuner know as soon as he comes back!

[tomm.brz]

ZA1JA01C is a US tune , while it s not wrong, unfortunately Racerom seems to bug the US tunes A LOT as I said earlier
Euro ZA1JA02G will fix everything as it works flawlessy with every racerom and ecutek featur
Your tune then could also need fueling and air calculation modifications
One time i helped a guy with an american car switching to A02G and maf scaling and fueling were messed up a lot when on boost

[steve99]

Originally Posted by Cebal

Yes, im in Europe and yes it's an import car but how do you know it's a US tune? Well, I have zero idea about tunes or tuning so I can't really tell which RR I have tbh. Unfortunatelly I dont have my previous tune anymore :/
Thanks for your help, Im gonna let my tuner know as soon as he comes back!

as Tom said there were some weird bugs with usa tunes if racerom 10 and 11 were used 9 and 12 seem ok


Also Deliceous tend to use a lot of custom maps to manipulate fueling and likely pi/di ratios. Very difficult to fault find if you dont have access to tune.


but as tom said very difficult to get big 1100 cc injectors to work at idle,


not sure why tuner would not use DI only at idle or its bug in racerom or setting in tune

[tomm.brz]

steve, it s just a bug, there is no custom map forcing 100% pi at idle,

i' m facing it both on A01C and B01C with racerom 12.1 ,
on idle it remains in fuel status 1 (not ready) and force 100% PI at idle , so the car jerks continually at low rpm


I update every us car I tune with Euro A02G