Peugeot:Citroen 1 6 HDi EGR Valve and Boost Issue fix

Fixing a 2007 Peugeot 307 1.6 HDi which was not running right. It arrived here in limp home mode unable to rev above 3000rpm and very slow on the open road.

There was no engine management light but plugging in diagnostic equipment a fault code ‘P0401 Air circuit quantity of air measured higher than the reference value’ was shown.
Using google to look into this issue most results allude to the EGR valve not working correctly. It was worthwhile having a look at the EGR valve.

Any decent diagnostic equipment such as Peugeot planet or other universal machines can read live data to see if the EGR valve is opening and closing this one was not. Also doing an actuator test to operate the EGR valve made no clicking noise indicating a potential issue with the EGR valve which meant it was worth removing the part to inspect it.

This lack of boost can be caused by a number of things the turbo actuator, the boost solenoid or the vacuum pipe joining the two. The easiest thing to check is turbo actuator by removing the vacuum pipe going to it, pulling the actuator arm back and putting a finger over the vacuum pipe inlet on the actuator. If it holds in position and only releases when the finger is removed then it is ok. If it creeps forward while the finger is holding the vacuum inlet there could be a leak, also if it doesn’t spring forward instantly when the finger is removed then the internal spring has went bad.

The next thing to check is the vacuum line between the boost solenoid and the turbo actuator. The boost solenoid is at the back of the engine in a rather hard to see place, but tracing the vacuum line back from the turbo actuator to the solenoid i could feel it was broke. Removing the vacuum line confirmed this. It was cheaply replaced with a new length of vacuum line/injector leak off pipe. It did involve working somewhat blind to get the pipe over the boost solenoid but once the boost solenoid and turbo actuator were connected the turbo actuator was moving the wastegate as it should and the car was running much better. Initially there was quite a cloud of black smoke as the turbo was boosting properly for the first time in quite a while. However after a few minutes the smoke cleared and now the car is driving very well.

All in a new EGR valve cost £50, a length of vacuum line cost less than £5 so this car which was close to being condemned for scrap is now driving as it should. It is problems like these that some simply dismiss as french shite however rather than being so dismissive over a problem actually taking an analytical look at the issue is much more productive and can keep a perfectly serviceable car on the road for a while longer. It also means that if you see one of these cars for sale cheap with this sort of problem consider buying it because it is a cheap and easy fix.