P0300, P0303, Rough Idle/Surging and Stalling, 2017 BRZ 6MT bone stock
 

2017 BRZ 6MT, 27,000 miles. Bone stock its entire life. Never tracked, driven very conservatively.

Just developed a super rough idle with lots of surging. I've only driven the car in this condition for about 10 minutes. At first it was able to idle when stopped for a traffic light, albeit with lots of surging and bucking and almost stalling. There didn't seem to be any power loss and the engine seems fine above 2500 RPM (though didn't go past 3500 RPM). It's just very rough 2000 RPM or lower. Eventually when I got home and let it idle for longer it stalled.

Have flashing CEL and pulled codes P0300 and P0303. Only thing I've checked so far is for a loose ground bolt for the DI computer and it seemed tight.

Any other ideas?

Could be as simple as plug or coil #3. That`s where to start looking as P0303 is a misfire in cylinder 3

P0303

P0300 is multiple cylinder, 030x are cylinders in order, so P0303 is cylinder 3

Yes #3 must have typed the wrong number and should have proof read it. It makes sense

Thanks all, will start with a plug and coil check on cylinder 3. Seems odd to happen on a completely stock car and with the 2017+ coils :iono:

Meh... It happens. Try swapping coil packs to see if the misfire code follows. In my experience with other engines/manufacturers, the multiple misfire code can be thrown if the ECU doesn't know where to place the blame.

I don't know how it happens specifically, but I have my theories about sample timing, resolution, sensor gains... blah blah blah

Just took off the coil pack for cylinder 3 (rear passenger) and removed the spark plug. Plug looked fine, but I got a new OEM one so put it in. Also took off the cylinder 1 (front passenger) coil pack and swapped it with the original cylinder 3 one. Started it up, no change to symptoms. Rough idle/surging. Didn't want to take it for an actual drive. Still showing P0300 and P0303 (I cleared it and it persists, so looks like the coil pack is in the clear).

I have an appointment at the dealer on Monday, but anything else to look at before then? Could it be an injector issue?

Might be fuel related.

Check manifold pressure at idle should be round 0.4 bar or 4 psi with just ignition on engine stoppedshohld read 14 psi or 1 bar


if the monifold pressure donest go down to arround 0.4 bar when idling you likely have intake leak


also check the long term fuel trim at idle if its way positive like 15-20% likely exhaust leak
see if afr ais stagle round 14.7 at idle when warmed up if not you got fuel issues. If its hunting up and down fairly quickly like to 16 then doen to like 12 its usually the 02 sensor cone bad

You did the easy part: move or replace the spark plug and move the coil eslewhere. If it doesn't move, then the problem could come from anything that didn't follow the park plug or coil. ANYTHING. Injector, coil driver, injector driver, wiring/connectors, or even engine mechanical .

Remember, you need 3 things to get boom: Fuel, Spark and Compression.

If you are bringing it to a shop, stop messing with it because you'll just make the guy's job harder. Doing the easy, non-invasive part was perfectly fine, but leave it virgin, otherwise it's a PITA to work around someone else's mess and makes discerning real evidence of a fault from "someone fucked with this before bringing it in" really hard. It can turn a straight forwards diag job with one root cause into a parts cannon job just to eliminate the uncertainties the previous guy introduced.

The tech is already going to redo what you just did anyway. Even if you tell him you did it, it's his job to do it again, because he can't take what you tell him for granted, customers lie, either by omission or ignorance and listening to them is a sure way to mess up. He has to let the car do the talking.

I recently experienced P0302, cylinder 2 mis-fire. And it was nasty bad.
Turns out the main electrode had broken off the nearly new (under 1000k) OEM Denso plug.
New plug installed and all is good. Now the search begins for better quality plugs. May explore a colder plug for my boosted application.

I’ve got P0300. Cylinder 3 misfires like crazy. Replaced spark plug and Coil pack and still misfires.

Taking it to dealership…

Also have P219A
P119F
P119E

Completely stock tune…

With the P0219a and P0119f codes the dealer is probably going to say the valves need adjusting. Google those codes. There are several posts out there including mine that can give you some insight. I was getting those codes on my 2013 FRS after a rebuild but had no other symptoms. My tuner disabled them. If memory serves, @RZNT4R has experience with the P0219 and P0119s.

Yeah but it's less likely on a '14 FR-S unless it's crazy high mileage and past due for a valve adjustment.

It's was a bad batch of engines in 17 and 18 that were adjusted too tight. But if a few thousands on a valve shim can trigger these codes... anything could...

Typically, it seems like the engines with tight valves would throw the codes but still run right. mine was like that: If I wanted it to set it had to be in extremely specific conditions of warming up from 10-12 degrees celcius, with the water temp up to 50-55C, at idle with no electrical loads or AC, it would idle ever so slightly uneven for those 40 seconds where everything was perfect and it'd store the code. Just having the lights on would put enough load on the engine to make the problem go away.

If you've got a cylinder constantly missing, then it should be easy to find the culprit.

Oops. wrong poster. You're right.



OP's car is a 17 with 27k. on the clock.

Yeah that's more in line with the valves thing.

Mine started just past 12000km, and in the huge thread about it, some people got the light rolling out of the lot. If that is his issue, OP is terribly unlucky that it was juuuuuuust tight enough to get this long for it to cause trouble, it's probably not under warranty anymore.

Mine failed under warranty and it took like 3 visits to the dealer and I eventually lost the car for a month. If I had to have it happen again outside the warranty, I'd go through the touble of checking the valve lash myself rather than bringing it to a dealer only for them to run around for hours going down the diagnostic flow chart only to come to the conclusion that they want to yank it out after throwing 8 injectors, an ECM and a injector driver module at it.

While the shims can't be changed in place, the lash certainly can be checked with basic tool while the engine is still in the car. It's not exactly "fun" if you've not mechanically inclined as it may still be daunting to take the valve covers off and there isn't a lot of room to work in, it may be necessary if OP wants to save literally thousands of dollars. If OP is mechanically inept, having the lash checked by a trusted independent mechanic is still going to be way cheaper and easier than going through the dealer's bureaucracy and paying their rate, but find a place that likes subarus, as some mechanics are scared of the big bad subaru pancake: They'll see the room they have to work in and turn you down on the spot. They're pussies, it's not that bad, if there's room to do plugs in there, there's room to wiggle a feeler gauge.

OP update:

Dropped off at dealer 8/18/22. Their initial diagnostics pointed to an internal engine issue (not ignition, not fuel injection). They were finally able to take the engine out of the car and open it today and found a broken valve spring (I don't remember if it was intake or exhaust valve) on cylinder 2. Original CEL code was P0300 and P0303, cylinder 3. Apparently "lucked out" that there doesn't appear to be any collateral damage or piston damage.

Unbelievable how a 1-owner, bone stock car with only 27,600 miles, never tracked or autoxed (or really even driven hard for that matter) could have this issue. I thought the valve springs were upgraded at some point before 2017? No misshifts ever, oil changed every 5k miles or less, driven very conservatively, always let engine warm up completely before going past 2500 RPMs.

I'll do a search on the bad batch of 2017/2018 engines, but if anyone has experience with this or can point me to threads, I'd appreciate it. 5-year powertrain warranty ran out 1 month prior to this. Working with SOA to see what they can do. Seems like a design flaw or workmanship issue that they should be on the hook for. 2017 BRZ 6MT w/PP.

Sure is interesting. Truly lucky it didn't drop the valve or fuck up the head.

There are almost no recorded cases of issues with 2017+ engines on this forum.
The springs were probably changed a couple of times over the years.
Bad parts make it into cars sometimes. You just had the horrible luck to get one of them.

Just an update for posterity and to put a bow on this thread since it was frustrating for me to search for threads and then read them only to be left hanging because other OPs didn't update with the issue resolution.

Recap: 2017 BRZ 6MT, bone stock never modified, original owner, 27.6k miles, all maintenance performed by the book, driven conservatively, never tracked. P0300 and P0303 misfire codes. I was 1 month past the expiration of my 5 yr powertrain warranty. It was not a spark or fuel issue.

The issue was a fractured valve spring (I didn't bother to ask if it was an intake or exhaust valve) in cylinder 3. Luckily the valve didn't drop and cause any further damage. The dealer removed the engine, opened the heads on both banks and verified the one spring in cylinder 3 was the only fractured one. They replaced all 4 springs and valves in cylinder 3 and reinstalled the engine in the car. Total cost for parts/labor/tax: $5044. For various reasons (dealer tech shortage, queue of other cars at the dealer, parts availability), it took 2.5 months from the time I dropped it off to the time I got it back. I actually had to buy an OEM catalytic converter gasket from eBay myself and give it to the dealer to enable them to reassemble everything because that part was on national backorder and they wouldn't have been able to obtain it through official channels for at least another month :bonk:

After painstakingly making my case, SOA offered a $4000 credit for the repair so I was out of pocket for the remainder. I received the car back a week ago and it ran fine for the 40 miles I put on it before I sold it to a well-known used car retailer.

Why did I sell? Well, how would anyone be able to trust the other valve springs that were not replaced? This was a bone stock car that was maintained and never abused. It must have been a bad batch of springs.

Why didn't I ask to have the other valve springs replaced? It may be just me, but I can no longer trust an engine after it's been opened and knew I was going to sell the car regardless. I wasn't going to pay more to get the other ones replaced.

Anyways, I love the chassis and handling of these cars but have had the worst luck with the turd of an engine that the FA20 is. I was ok with the fact that it makes no power, no torque, has a torque dip, isn't smooth, doesn't sound good, etc... but to also have it be unreliable is just :mad0260::brokenheart: The BRZ was actually my second twin. I also had one of the first 2013 FR-Ss to arrive in the states, also kept it bone stock, maintained it well, tracked it 4 times and it broke a valve spring (it was one of the early casualties to the issue that we all now know as the J02 recall) and dropped a valve after 35k miles (covered under powertrain warranty).

I love the 2nd gen GR86/BRZ but just can't get myself to go for one after all this. But hey, maybe 3rd time's the charm? :bellyroll:

You might wait and get a 2023 or 2024 model. Hopefully, they will figure out the pan sealant issue by then.

On a 2014 it's likely a bad engine wiring harness....there is an updated version, plus updated coils availableut due to those codes.