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.