Rebuilt engine cam issue (P0019/P0021)
 

Hi All,
Need help diagnosing strange behavior after a rebuild.
MY15 BRZ - rod knock started a couple months ago at 36k.
The Decision was to rebuild the engine using an OEM short block, refurb and clean heads, gasket kit, new plugs...

Last week the engine went back in but had issues starting - turns out the cam chain was not put on properly due to wrong instructions sent by Subaru (at least that is what the shop is claiming).

The Engine came back out, another expert was called for help and this time the car started successfully. No issue running, oil flushed after the first heat cycle (decided to switch to Millers 5W30).
Unfortunately it was not all happy days, P0021 and P0019 errors popped up. Sensors and valves were swapped sides but the codes remained the same.

Second issue was detected during a test drive. There is a slight vibration/tapping noise from the chain/valvetrain when off throttle above 2k rpm. After experiencing rod knock, all noises like that give me chills...

Apart from that it is running fine, no issues idling or accelerating. I am not pushing it above 3-3.5k rpm as it is a brand new short block but seems to drive fine apart from the noise. I cleared the DTCs, went for a drive and they did not come back (yet?).

My mechanic is suggesting to drive it for a bit, until the oil change in 1-1.5k. Then decide if we need to replace the cam chain with a new one (old one was put back on after rebuild) and do further diagnostics on the error codes if they persist.

I am however not convinced. At this point I have no clue if the suggested new cam chain will really solve the issue and what's more if it's safe to keep driving it.

Any experiences like that or advice on what to check?

do you have more details on how the cam chain wasn't installed properly?

my first suspicion anytime a code pops up in a case like this is the sensor. it sounds like you tried checking this by swapping the sensors on each side.

i'm not fully convinced that a sensor wasn't damaged, but i'd also be wary of assuming that the timing chain is fully installed correctly if you're getting odd valvetrain noises. iirc, the tensioners aren't always re-usable, so if they're re-using it from the 'incorrect procedure' method, it's possible they damaged the tensioner removing and reinstalling it.

I recommend you stop driving the car and find a new shop to work with that is more familiar with FA engines. P00019/00021 is not one you want to ignore and drive around on.

nope. I don't know how long it takes for those IPVs to slew out, but I'm thinking new ECU at this point. OP needs a guy that knows techstream to be certain.

Thanks for your suggestions - I will definitely stop driving it and try to resolve this.

Would you say that the next step should be to redo the timing with a new chain and tensioners?
Hoping that solves the noise issue at least. If the DTCs persist, then the old chain/timing/tensioners could be excluded from the list of potential causes...

Also, I've read that there has been a TSB for sensor clearance, probably also worth checking right?

BTW finding a local shop with any experience with FA motors has been difficult - even the official Subaru dealer/service said they have never done this sort of work when I reached out to them for a quote.

Could you please explain a bit why a new ECU would be needed? Just trying to understand this. How is that required after a purely mechanical repair?
Is there no way to reset/flash the ECU back to 'factory' settings?

Ah, but the system is not purely mechanical. Each time the engine is started, the VVT servo system goes through a test, and calibration cycle. There is a table in the ECU ROM that cannot be edited via "normal": methods. None of the expert hackers have published, or maybe even discovered a way to access it.

First the VVT servo does a sanity test to verify that it knows approximately where the camshafts are relative to the crank. If it is reasonably close, it sets an "ok" flag and goes through a calibration cycle which updates the initial position value for each cam.

If the saved initial value swings too far out for whatever reason, when the root cause is suddenly corrected, because the saved initial position is always applied, the system never passes subsequent sanity checks because it's too far out of whack.

I don't know why it was done that way. The flawed logic is a severe handicap for the system but here we are.

I hope it's not the case for you. Techstream would give us a conclusive answer in minutes.

I'd say, it would be a good idea to verify timing. It's possible you have timing off a tooth on one, or multiple places, that could potential cause both those codes. There are two chains, 4 cams, plus the crankshaft sprocket. A lot going on in there.

Damn, reading through the forum and all the posts regarding cam timing DTCs sure is depressing. I Was really hoping that replacing a shortblock would be the end of my nightmares with this engine...

I've checked with the workshop a bit more and they have already tried swapping around the sensors and ocvs, the same P0021 kept popping up.P0019 was logged when they initially put back the motor with wrong timing.

@Ultramaroon thanks, really appreciate your explanation. I can see now that there really seems to be this issue where an ecu gets stuck with wrong learned values. Coming from a SW engineering background, it still baffles me that it's been released like that.

A couple more questions that trouble me:

1. How to check exactly if the learned values are too far gone? Is it Intake=62, exhaust=88 +/-10deg as per the 02-163-16R service bulletin?
2. Would you change the oil back to 0w20? I switched to 5w30 as a measure to protect the engine better at higher temps, but maybe this caused some pressure change to the vvt?
3. Is there a way to verify timing without disassembly? Seems unlikely that it's off because the car runs and idles just fine, but always better to make sure.
4. Could these issues be linked back to rod knock? Or would it be timing assembly related? Cam gear failure would be an unlucky coincidence right?
5. Is SSM equivalent to techstream? I am asking because I can get someone familiar with it to help out.

Don't let it discourage you. Once it's in order, it works beautifully. I'm not familiar with SSM but I imagine that all the same information can be extracted.

VVT hydraulics aren't significantly/functionally affected by oil viscosity. There's a lot of misinformation out there. I've given up correcting stuff every time I see it. This thread is old and long but it is where I spent most of my time helping/learning.

The ECU might still be ok. Don't swap it until you're certain.

this is where i'd start.

you already tried swapping sensors, which should rule out most electronic problems. yes, you could have 2 bad sensors, or a bad ecu, but they're much more distant possibilities.

my current vote is that there's a mechanical error in the system.

Leave the oil, isn't going to make a difference.

Looking at it, you may be able to verify timing by pulling the OCV's and turning the crankshaft pulley. Just be careful with the aligning the keyway with the crankshaft extension and oil pump or you could damage parts. Ultra has the service manuals in his sig.

You could potentially have a plugged OCV filter. These are in the head and are held down by the cam carrier assembly. You also could have debris affecting the cam gear and not allowing it to cycle properly.

I believe SSM is similar to techstream. Both should show you the cam timing values. You can go through the check procedure in the manual.


Edit: I just went out and checked and you CAN see the cam timing marks on the sprocket with the OCV's removed. So verifying timing without pulling the engine apart looks possible.
https://uploads.tapatalk-cdn.com/202...ed06a684ca.jpg

This is the third cool trick I've leeched off of you. First was the homemade guide pins for the timing cover. Second was the cardboard screw holder shadow board.

I honestly wouldn't have thought to check if the OP didn't ask. I thought the timing marks were farther out on the sprocket.

Many thanks for all the helpful tips!
Gives me a bit of hope that I can finally enjoy the car.

I'll schedule some time with a tech who knows SSM. We'll verify the timing and go through the procedure. I'll report back what we find :)