'17 308 GTi - Boost problem

[R99SWL]

Hi there,

Just found this forum, if you're on any of the GTi Facebook groups you may have come across my several posts in regards to this!

This may take a bit of explaining, so bare with me! In a nutshell, my car isn't boosting above maybe 4psi if I'm lucky. It's a 2017 (pre-facelift) 308 GTi 270hp with the EP6FDTR engine.

June: The LSD disintegrated and wiped the gearbox out with it. It was too damaged to economically repair, so I had to wait for a reconditioned unit from Peugeot to become available.
July: Reconditioned gearbox & LSD is fitted. The following week I spent babying the car about to let the gearbox bed in. At one point, I accelerated on the motorway in 6th gear to overtake a vehicle, and the car felt noticeably underpowered and throws itself into limp mode. Restarting the car cleared limp.

I took it back to the garage who did my gearbox, they plugged it in which produced the following codes:
> P2262:00 - Turbocharging air circuit. Compressor discharge solenoid valve suspected stuck in open position.
> P0299:00 - Turbocharging circuit - Mechanic fault.

They advised me that the compressor discharge solenoid valve was essentially referring to the dump valve. So I swapped it our myself for a Forge unit. It made no difference. At this point I was virtually broke from the gearbox repair, and couldn't afford to keep going back to the garage for diagnostics, so since the car was running fine and simply not boosting, I had to leave it for the time being while chasing things down as best I could - I'm not very mechanically minded. At this point on my own OBD2 Bluetooth scanner it is producing no codes.

I was advised by a few sources that the boost solenoid under the intake manifold was relatively well known to fail and could be the source of my problem. So I ordered one, and with the help of a friend (also a 308 GTi owner) we swapped it. Again, it made no difference. He had a paid software (ThinkDiag) so we used that to see what codes that was producing. They were:

> P0299: Air Inlet Circuit. Air Turbocharging Pressure lower than the reference value, Legislative Theshold Intermittent
> P0098: Inlet Air Temperature at the Air Inlet Manifold Inlet. Voltage of component too high Intermittent.

(Also present but unsure if relevant are P0610 - Fault in the configuration of the ECU & P160A - Configuration fault of the approval number).

I was informed at this point that there isn't a sensor for the IAT and it was calculated using both the MAF and MAP sensor. Now, I have previously had one of the wires leading into the MAP sensor plug snap, and so I had it repaired at my work (I work for an unrelated dealer). Unbeknownst to me, they'd given it to the apprentice who'd basically soldered it to the plug and heatshrinked it. When I saw the state of the wiring, I assumed this was the cause of the voltage code. So I had a new plug properly installed and this did actually remove ALL codes... for a short time. And guess what? Made no difference to the boost whatsoever. And the codes came back the next day. I've also previously had to clean the MAF sensor as it went dodgy not long after I bought the car, so I figured maybe it was worth replacing both the MAF and MAP sensors. As usual by this point, it made no difference.

So at this point, my work had just hired a new tech from BMW, so since he had a bit of familiarity with the THP engines I was able to get him to spend an hour or two inspecting and seeing if he could find anything. He pressured tested every accessible line, and everything seemed fine. The actuator worked as it should, turbo seemed absolutely fine, put a 3-piece on the vacuum lines and everything built pressure as it should. The only thing he found odd was that when he put a 3-piece on the line leading to the actuator and put his thumb over it, it would build pressure to the expected amount, just slowly. Put that line back onto the actuator, and it would only build a little bit of pressure, nowhere near enough. However, he couldn't find any reasoning for this and was a bit stumped.

So back to square one. One of my mates offered to smoke test it for me, so we spent a good couple of hours testing all the pipework. Absolutely no signs of a leak except for some smoke coming from the PCV valve. So I changed that too! And shocker, no difference at all. I was later told that smoke coming from there was actually normal if it had nowhere else to go, which it wouldn't have done when we tested it as all open pipes were bunged up.

So since everyone was absolutely stumped, I took it back to the garage who did my gearbox just last week to have another look. They spent a good 4 hours on it, and called me in frustration. They'd found nothing and were totally baffled. Their machine was coming up with the same codes as when they first plugged it in. The only thing they said they found strange was that when they tried to access the boost solenoid directly on their computer, it was coming back as 'no signal'.

So essentially that's where we're at. I'm not mechanically minded enough to tear it apart or trace down any possible electrical issues and I'm really at a loss. The Facebook groups are a bit stumped too! Being flat broke from the gearbox fiasco doesn't help my cause unfortunately.

I've recorded a live data 1st - 2nd - 3rd gear pull using the Torque app & Bluetooth OBDII reader, if it's of any use! It's unlisted but should be visible on this link:

Other things worth mentioning:
> There was a period of time where if I very very slowly rolled onto the throttle, it would randomly give me full boost maybe 3 out of 10 times I tried. However, it hasn't done that in a good 2 months now.
> It will go into limp if I push it too hard, particularly in 5th and 6th. It's done it once or twice in 4th, once in third and never in 1st or 2nd. Limp always only puts the SERVICE light on and always clears when I restart the car.

Any input would be massively appreciated! There's very little in regards to the P0098 code in particular online, if anyone could expand upon that it would be interesting!

Many thanks,
Adam

[xantia_v6]

I think that the best diagnostic is to measure the vacuum at the wastegate actuator when putting the engine under load at reasonable throttle. If there is less vacuum there than expected, then you should be suspecting a blockage in a vacuum hose, or a bad vacuum pump (assuming that the new control solenoid is OK).

The other thing which does not seem to have been explored is a leaking wastegate valve. I have hear of them failing on Mini Coopers, leading to low boost. Did the smoke test check that?

[R99SWL]

Thanks for your reply! This is where my lack of mechanical knowledge is unhelpful... I know they vacuum tested the line which leads into the actuator, if that's what you mean? That was with the engine idling.

Where is the wastegate valve please? Is that different to the dump valve? Sorry for my lack of knowledge, I'm learning as I go!

[MarkusSA]

Hi All,

I also have a Boost issue on my DS5 200THP.
P2263 according to Diagabox.

I have changed the solenoid valve underneath the intake, also replaced the solenoid mounted to the turbo and also have a DV valve between the solenoid and turbo to keep things lasting longer.

But still no luck with getting boost, if i exceed more than 3000rpm or need full boost it takes boost away immediately.
I will attach pictures from scan.

PS: when i start the car and measure vacuum at turbo waist diaphragm i get -20 on the gauge.

[xantia_v6]

Thanks for your reply! This is where my lack of mechanical knowledge is unhelpful... I know they vacuum tested the line which leads into the actuator, if that's what you mean? That was with the engine idling.

Where is the wastegate valve please? Is that different to the dump valve? Sorry for my lack of knowledge, I'm learning as I go!

Sorry I missed your reply.

The wastegate is different from the dump valve. The wastegate bypasses the exhaust side of the turbo to regulate the boost pressure. It is controlled by the vacuum actuator, but the valve itself can get damaged and cause low boost. The wastegate valve is inside the exhaust end of the turbo body.

The dump valve bypasses the intake side of the turbo, but is an on/off device and only opens when the throttle is closed rapidly to prevent pressure spikes .

[xantia_v6]

Hi All,

I also have a Boost issue on my DS5 200THP.
P2263 according to Diagabox.

I have changed the solenoid valve underneath the intake, also replaced the solenoid mounted to the turbo and also have a DV valve between the solenoid and turbo to keep things lasting longer.

But still no luck with getting boost, if i exceed more than 3000rpm or need full boost it takes boost away immediately.
I will attach pictures from scan.

PS: when i start the car and measure vacuum at turbo waist diaphragm i get -20 on the gauge.

That is similar to the symptoms I had when the atmospheric port filter on the boost control solenoid was blocked, but it would only throw the fault code occasionally.

[MarkusSA]

Could an over boost error be caused by a Faulty turbo?

Because if the turbo was faulty, it would not build boost at all.......

Another concern, Reference intake pressure vs measured intake pressure.

The one on my car stays almost close to 800 whilst the other one changes as I REV the motor.

[Disciple82]

Hi new to the thread and forum.

I have a 207 thp. Even though this is a different car you guys already know its the first prince engine. I have the same symptoms as you. Not developing boost but the turbo is whining loudly where its spooling. Have had codes for over boost (I caused this) and the same codes you've had in this thread low boost and also dump valve is stuck closed.

Coming back to the overboost code I plugged a vacuum breather pipe that runs round the side (timing chain side) which I believe allows the vacuum system to release vacuum. It caused the turbo wastegate to vacuum shut but wouldn't then open. It caused a loss of power even more than its lost at the moment. Removed the plug and it was back to its normal/underpowered self.

I know this is a long read but here's what I've noticed about my engine. It has normal power between 1k and 2k revs but as soon as the turbo should kick in it doesn't. I've noticed the turbo is spooling really loudly even after 2k revs but if you use less throttle it seems like there's more power not much but their is. I have put this down to over fueling.

I can't hear any boost loss but there are little flutters of boost sometimes in 2nd gear at the start of the rev range like something is retarding the power. I am going to send it into a puegeot time served lad. He'll probably do the same checks that you guys have already done but I've read on another forum that the chain stretches and the intake cam causes the synchronisation to go out of time and cause power loss.

[func98]

Hi All,

I also have a Boost issue on my DS5 200THP.
P2263 according to Diagabox.

I have changed the solenoid valve underneath the intake, also replaced the solenoid mounted to the turbo and also have a DV valve between the solenoid and turbo to keep things lasting longer.

But still no luck with getting boost, if i exceed more than 3000rpm or need full boost it takes boost away immediately.
I will attach pictures from scan.

PS: when i start the car and measure vacuum at turbo waist diaphragm i get -20 on the gauge.

That is similar to the symptoms I had when the atmospheric port filter on the boost control solenoid was blocked, but it would only throw the fault code occasionally.

I have the same problem as yours. Has it been resolved? If so, how?

[gwest]

Problems with camshaft timing can often throw up spurious turbo fault codes, as happened recently with my RCZ THP200. But you need a code reader that lets you collect and plot live data (Launch 123e was used ). On a previous scan I had a P0012 timing fault.

This was traced to a 'lazy' camshaft solenoid valve. I have solved these problems in the short term by standing the solenoid valve in a jar of kerosene placed in an ultrasonic bath, and changing the kero until it stayed clean. Merely spraying the outside of the valve is unlikely to be effective.