2012 308cc EP6CDT Running Poorly- Intermittent

[Remington]

G'day all and Happy New Year.

I was hoping somebody who has more experience with these French cars could perhaps throw a few intelligent suggestions my way?!

The car is a 2012 Peugeot 308 convertible with the 1.6L turbo petrol engine (115kw with 6 speed auto transmission). Traveled about 115000 klms.

The car is owned by my sister in law who doesn't live all that close to me, so that adds more issues to to these on going problems.

She bought the car around 6 months ago with around 112000 klms on the clock. She had no issues for about 1500 klms of driving and then messaged me about the engine running rough. She explained it had little power going up hills with check engine light showing. She called the roadside guys who came out and looked at it, scanned it and showed her the codes, then cleared it and it appeared fine. The guy told her it was more than likely coils and plugs, not uncommon etc etc.

She brought the car over to me to look at and I told her we'd do an oil service, change air and fuel filter (looks like this car doesn't have one?), change coils and plugs as they aren't very expensive and almost a service item on Euro cars.
New Bosch coils and plugs and other quality parts were used. The old coils had a date code of 2017 on them.
Car was finished and taken and she messaged me later saying it sounded great and drove well.

Unfortunately, about 1000 klms later.... the car ran like junk again. It was similar to last time, she was going for a long drive and it began playing up under load on hills etc. That time she had the car towed to me so I can have a look.
Sadly I only have a cheapo scantool and did see a code which cleared and then the car ran perfectly fine after the codes being cleared. That wasn't what I wanted as I hoped for it to have a hard fault that I could trace. The code that showed was a P0299. The scantool didn't have the description in the database.

She took the car and drove it for about 500 klms and told me it played up again... same story- rough running, engine light etc. She had the car towed to me and today I had a quick look with the scantool. There were a few codes P1336, P1337 and P1339 (no descriptions with my tool). A quick Google showed misfire codes and a mention of misfire cyl 1. I had the engine running and it was definitely misfiring as I pulled number one coil plug off and no change. Pulled number 2 and the engine stalled. I then swapped coils over and cleared codes and of course the engine is running fine now. I know if I release the car to her, it will play up again. I'm getting sick of thing as it's all basically a love job and I told her not to buy the car in the first place!

Now, I see that these engine have issues with high pressure fuel pumps... I don't think any of those codes are related to it? Also, timing chain issues- sounds ok on first start up? Turbo problems.... don't think those codes are related? Carbon build up on valves- wouldn't that be all the time and not intermittent? Can't see any obvious air leaks or split hoses but I haven't done anything thorough yet.
So please.... has anybody ( a tech? ) seen this problem in their shop, or an owner who has paid too much in getting this problem sorted?

Any help is greatly appreciated and sorry for the long first post... I go a little crazy when it's way past my bedtime!

[xantia_v6]

What grade of fuel do you have? In NZ the best universally available fuel is 95 RON and our 308CC is not happy with it, throwing random engine codes (misfire and knock) going up hills. For the last few years I have filled it with 100 RON (available a a few stations) and no more knock or misfire codes.

BTW, ours does not have a fuel filter either.

[Remington]

Sorry, forgot to mention earlier... She had filled it the first time with E10 which is crap fuel with ethanol in it.
I told her to NEVER use that fuel and only use 98 RON.
She has since used both 95 and 98 RON which is the premium fuel here and ethanol free. I'm sure the fuel lid states 95 RON minimum.
I suppose I can throw a bottle of octane booster in the tank for shizz and giggles.

[PaulC5]

Some of the codes suggest the high pressure fuel pump can be the problem viewtopic.php?t=69347

I had P0299 on our C5 and it was the MAP sensor was bunged up with oil/carbon giving a suggested low boost pressure - a new sensor fixed it but first I checked the live data and saw its value was not changing much.