VVT Not Enabled

[tomm.brz]

well i hope not, they are new too and my mechanic work as a subaru dealer since 35 years, and did open and closed hundreds of engines and more than 20 (in italy we have very few of them) brz/gt86, also did some recalls and no one had problems yet, other than me
so i like to assume he can put sealant in a good way, I hope

the cam was oscillating like the video i'm posting from the first crank after the rebuild, that makes me lean toward a cam gear problem maybe?

Sorry for the music in the video, you can see the cam intake #1 oscillating a lot, cam int #2 works much better and cams exhaust work perfectly

vvt hasn t activated again after a restart, as I predicted
the only way to activate it is, other than luck, reflashing and starting with oil under 20 Celsius, do a lot of engine braking and blipping hard
But cam int #1 other than oscillating, reaches absurd values like -20 or -15 when the maximum advance from table is -10

[tomm.brz]

No wait, those on videos are totally working
i was just standing with my car and blipping randomly but if i was driving you would have seen all the 4 cams working pretty good
the oscillating of cam intake #1 is present only at idle and light load/low rpm
But if i drive strong they totally follow the targets
if vvt is not working, they stand still at 0 all the time... my main problem is that they indeed fail to activate most of the times

I have a small log saved in my radio, showing better the 4 cams working good, i'll post it tomorrow cause it s 2 AM here now

[tomm.brz]

i have 0w40, shouldn t be too thin but can be

Anyone has other ideas what could bring this oscillating issue? if it s a real mechanical problem or electronic/sensors/ocv?

[steve99]

Originally Posted by tomm.brz

But when i first checked the VVT initial value it gave me 0.0 on intake side
but then the morning after (yesterday) it activated anyway after a reflash?
Can it go bad and then suddenly works and then bad again?

Today no luck, the vvt angle goes to 0 when oil is warm but doesn t activate.. they seem to move a little bit if i blip the throttle, like 1-2 degrees of movement but stay off

i have a tactrix, but i Don t know where to source an ecm here in Europe, they seem all so expensive

There are lots on ebay they are all same 86 brz frs auto or manual just flash it with correct calibration with tactrix then sync to security
https://www.ebay.com/itm/2016-SCION-...edirect=mobile

[tomm.brz]

yes i understood, i even found one at 137€ shipped and taxed
but yesterday vvt started

don t you think if ecu were toasted, it could never started?

see post #58, when it starts, if i Don t turn off engine, it works perfectly under high load, never fails to command the angles and follow targets

it just oscillates at idle and low loads

i would think if ecu is toast it could never work good

[steve99]

Originally Posted by tomm.brz

yes i understood, i even found one at 137€ shipped and taxed
but yesterday vvt started

don t you think if ecu were toasted, it could never started?

see post #58, when it starts, if i Don t turn off engine, it works perfectly under high load, never fails to command the angles and follow targets

it just oscillates at idle and low loads

i would think if ecu is toast it could never work good

Yes seems unusual


Maybe check cam sensor clearances as per the TSB, its fairly simple check\fix


The tsb is on rhis forum in TSB section think it one for rough idle

[tomm.brz]

point is, i do not have a rough idle, nor a CEL

after built the engine, we started it vvt enabled right away when oil reached 32 C
and cam int #1 started oscillating like per video

after 40km it fixed itself and worked perfectly for 600km

then started not enabling anymore and when it activates, it oscillates and slowly oscillates less the more i drive.. but when i stop the engine, it struggles to activate

The sensor were signed and put in the same place, and being a 2017 i find difficult the clearance modified by itself with no reason

[MobiusOne]

Originally Posted by tomm.brz

point is, i do not have a rough idle, nor a CEL

after built the engine, we started it vvt enabled right away when oil reached 32 C
and cam int #1 started oscillating like per video

after 40km it fixed itself and worked perfectly for 600km

then started not enabling anymore and when it activates, it oscillates and slowly oscillates less the more i drive.. but when i stop the engine, it struggles to activate

The sensor were signed and put in the same place, and being a 2017 i find difficult the clearance modified by itself with no reason

Did you spun a bearing? Did you replace all the components that got in touch with the oil?
Seems like a mechanical issue to me... maybe the avcs cam pulley. Without the correct tools you can damage the pin that allows the rotor to spin. This pin moves according to the oil pressure and if damaged during assembly/disassembly you can have weird cam behaviors.

[tomm.brz]

I threw a rod through the block and changed ALMOST everything... only thing i didnt change is the cam gears unfortunately
Mechanic is a subaru dealer and knows how. to work in a FA20, not his first time

So maybe yes, it s the cam gear of cam intake #1, because sometimes it works super good and sometimes doesn t even activate the vvt

[tomm.brz]

So, ecu is ok. That thing that you must change ecu if initial values are off was too strange to be real, in fact now:



I managed to activate vvt pretty soon, cranked a bit the engine longer with fuel cut to let pressure oil build and then after a few engine braking it activated, oscillating like crazy

I read vvt initial values, getting this on the photo and proceeded with the active test
cam intake #2 responds quick and well
cam intake #1 responds a bit crazy, because it oscillates but still responds positively

That brings me to exclude cam sensor and OCV, they work good.

The problem i think is really the cam gear unfortunately, Nd/or the engine oil

I went for a drive (log here in the bottom) and on load, the cam #1 responds super good after a good drive, it just oscillate a little bit during low load

after this long drive, vvt activated no problem also after a second engine restart

Since my oil cooler doesn t allow me to go more than 89 Celsius on engine oil, i m afraid my engine oil is a bit contaminated by fuel... does it make sense?

I will change oil and cover more the cooler, I want my oil to go over 100 Celsius

https://datazap.me/u/tommbrz/vvt-1?log=0&data=12

[steve99]

Originally Posted by tomm.brz

So, ecu is ok. That thing that you must change ecu if initial values are off was too strange to be real, in fact now:



I managed to activate vvt pretty soon, cranked a bit the engine longer with fuel cut to let pressure oil build and then after a few engine braking it activated, oscillating like crazy

I read vvt initial values, getting this on the photo and proceeded with the active test
cam intake #2 responds quick and well
cam intake #1 responds a bit crazy, because it oscillates but still responds positively

That brings me to exclude cam sensor and OCV, they work good.

The problem i think is really the cam gear unfortunately, Nd/or the engine oil

I went for a drive (log here in the bottom) and on load, the cam #1 responds super good after a good drive, it just oscillate a little bit during low load

after this long drive, vvt activated no problem also after a second engine restart

Since my oil cooler doesn t allow me to go more than 89 Celsius on engine oil, i m afraid my engine oil is a bit contaminated by fuel... does it make sense?

I will change oil and cover more the cooler, I want my oil to go over 100 Celsius

https://datazap.me/u/tommbrz/vvt-1?log=0&data=12

Agree
Intake cam#1 looks like issue low initial learn and unusual readings when running. Maybe swap the ocv cam 1 to 2 and retest then swap sensor 1 to 2 retest just to be sure..


Unfortunatly it could still be an intermittent input/ output channel on ecu or as you say the actual cam gear. Very difficult to accuralty diagnose these cam issues

[tomm.brz]

i will keep my idea that it s not the ecu
i carefully watched the cams on the radio while driving, and as you can see in the log it's not bad at all and not intermittent... just seems to swing around the target when engine load is very low

that behaviour started immediately after the rebuild, nothing makes me think of a sudden failure of ecu, cam sensor or ocv.. but a failure of the cam gear is very plausible
the cam connected to it, got a bend of 1 degrees.. it surely got a heavy shock

I would not accept it because it s annoying to fix now, but let's be real... it s very plausible

The fact is, if vvt enables, it s not annoying because whem i'm driving it s good.
For now i will try just changing the oil, keeping it good quality covering the radiator so that it can go over 100 Celsius (my catch cans are always empty) and see if it s acceptable.. and if vvt keeps enabling
if not, i will change the cam gear (i m annoyed by mechanic that was saying they looked good and didn t want to change it to be honest... i even asked him when engine was apart)

Will keep you updated, and sorry for the thread hijacking

[DarkPira7e]

Thank you everyone for your time troubleshooting! I haven't had a lot of time to try anything aside change the oil (just changed it, but it's 18:30 and dark here so I won't drive it tonight).
I'm working with my local protuner VEMS to diagnose and fix this issue.
He found that the following requisites are listed in the service manual as all needing to have been met-

Battery voltage of 10.9 or more
Elapsed time after engine start of 60 seconds or more
Coolant of 50c or more
VVT target less than 0.01ca
Learning experienced flag reads "Set"
Duration of no power steering switch change - 3 seconds or more
Duration of no clutch switch change - 3 seconds or more

I'm sure there are more conditions that are situational.

[tomm.brz]

Today i got it working all day, no problems

Just a bit of oscillation from cam intake #1 that actually fixed a looot after 1 hour with oil pretty warm

I found this page: https://www.armstrongfamilyblog.com/...elation-p0018#

the autor thinks the vvt initial values are burnt PERMANENTLY into ECM, with no going back Then on the comments at the end you can read:

" That’s a good question, the only answer I got regarding this from the SUBARU field engineers is:

the first time a new ECM runs the engine the Exhaust cam values are burned onto a ROM chip and used for reference. The Intake values are learned on the first drive cycle.

It’s a lame design"

That explains why after a reset and reflash I get 0.0/0.0 on Intake initial values but good values on ehxaust
But it makes no sense because if that was true, i couldn t be able to even get those 0.0 and able to get the vvt enabling again!
So it seems obvious to me that the step of replacing ECM is useless and a simple reflash can take care of the vvt initial values

My car is driving good, i do not want to change the cam gear as it is too expensive and laborious, i Think (if it doesn t get better aftet the oil change, and a swap of the OCVs from bank2 to bank1) I will play a bit with the "VVT OCV duty correction" table relative to the cam intake #1, to remove or reduce the oscillation
It sounds to me like an over-doing of the closed-loop integral correction of it, kind of like when you try to make the electronic boost controller to follow the boost target in a Turbo application, and the final boost start to oscillating through the target instead of being steady


edit: my oscillation seems gone apparently, also vvt initial values are a bit better now, 57 / 61
I stopped babying the car and now it is getting better!