This is what I am doing at the mo to fix the small faults with the engine .
Direct injection engines, such as the EP6-DT and EP6-DTS by Peugeot/Citroen,
suffer from combustion residue buildup on the intake valves. Because fuel is injected directly into the combustion
chamber, it does not go through the intake manifold to
clear the valves - as would happen with an indirect injection engine.
Oil residues on the valve stem builds up and becomes solid over time.
The solid residues cause loss of power because they block air flow through the
engine.
The extent of the problem can be easily seen with the valves removed from the engine.
The valves have change shape because of the residues.
They have now become cones, blocking airflow.
Exhaust valves have no such problem because exhaust
gas flows at very high temperatures.
Comparing a used valve with a cleaned one.
Stopping oil from getting into the intake manifold directly from the crankcase
The latest and greatest modification for getting rid of oil in our intake manifold, which is causing so many problems in the cylinder head and intake valves, comes from Peugeot themselves.
The new RCZ and 308GTI with the THP200 engine have a small difference in their intake manifold compared to the older models.
While the manifold body is the same, there is a very small cap that closes the rear PCV hose in the THP200 engine, which does not exist on the THP150 and 175hp engines.
PCV is the Positive Crankcase Ventilation system, which forces blowby gases back (and a lot of oil coming with it) in the intake system.
This cap is very cheap and available from Peugeot (part code
0361S4 ), using it saves the trouble of having to clean your intake from oil and combustion residues.
The difference between the intake manifolds can be seen in the following pictures from Peugeot Servicebox.
Part number 8 is the cap that closes the PCV return hose from the engine to the intake manifold.
Installing the cap in THP150 / 175 engines
First remove the rear PCV return hose. Press the clip to release it from the engine cover.
Intake manifold side
Press the clip on the intake manifold to release the hose again.
The cap that solves our problems
Remove the hose from the engine bay.
Install the caps
Both caps installed, no more oil in the intake manifold.