HDI power loss

[UncleBen]

Hi all.
Firstly I hope this finds everyone in good mental and physical health.

I wanted to pass on some information regarding intermittent power loss which I recently experienced. The car would sometimes not pull well, weather it be on a flat road or up hill. I came across a post from back in 2015 which pointed me in the right direction :Poor Performance on 2.0HDi
I found there to be 2 control solenoids the same, mounted next to each other. These were located on the back of the engine at the top left as you look from the front with bonnet open, and extremely hard to access. To replace them I needed to remove the O/S engine mount and drop the engine, then it was mostly done by feel. I had no idea which one was at fault so I replaced both. Now the car is running great again, power and torque as before.
Going back to the post I mentioned. The air doser was spoken about, which led me to look at my set up and try to understand it, I haven't understood it as yet and would appreciate some clarification if anyone knows. I think I'll start another post on this as this one has gone on a bit.
Thanks guys, stay safe.

 

[Pedro]

Air doser works like a butterfly valve & regulates the air flow its usually fitted between Intercooler & Turbo some Diesel engine owners just clean it & that seems to cure the problem you may need to inject something like a DPF cleaner to shift all the dirty deposits which build up over time

 

[UncleBen]

Hey Pedro, thanks for replying.
I didn't make it clear because I intend on starting another topic on it, I'm not having any issues with it, I was just trying to understand how the system works. Because there are two butterflies, one from the intercooler which has a plug and vacuume connected to control it and one which is a bypass, that has no electrical or vacuume connection. What is very puzzling is that the bypass butterfly is always in the open position, which means the engine is always drawing in a certain amount of air which has not passed through the intercooler.

 

[Pedro]

Hey Pedro, thanks for replying.
I didn't make it clear because I intend on starting another topic on it, I'm not having any issues with it, I was just trying to understand how the system works. Because there are two butterflies, one from the intercooler which has a plug and vacuume connected to control it and one which is a bypass, that has no electrical or vacuume connection. What is very puzzling is that the bypass butterfly is always in the open position, which means the engine is always drawing in a certain amount of air which has not passed through the intercooler.

Correct me if I'm wrong but the HDI has twin butterfly valves controlled by a actuator & vacuum system when they start to falter it might be a rack & pinion which operates the valves is on its way out that could explain why the Bypass valve being permanently open

 

[UncleBen]

Correct, it has twin butterflies but they are in no way mechanically connected, the by pass has no control attached to it, it is permanently open and that's what is puzzling.
The car is running great now but id like to understand how that system works.

 

[UncleBen]

I should say it is not stuck open, it is held open by a spring. I can close it with my finger but it just springs open again.

 

[Pedro]

Yes I suspected it may be different on your engine on other Peugeot variants it can be controlled by the rack/pinion system as for the flap it may operated by the Forced Air pressure design ie when the Engine is under load then probably it opens/closes to control the volumetric air intake whist combusting