
Now this happened 6 months or so ago, I fiddled a bit, changed the air filter and it went away a day or so later and didn't come back



Considered my options - service due in 500 miles, so do it now - changing the air & fuel filters might help.
Had a quick trawl on the web, particularly those fine, upstanding gentlemen on the 406 Coupe forum, as they have rather more 2.2 Hdi's, (aka tractors), than we do here on the proper site.
Now it seems others have had similar issues, oft mis-diagnosed as something really expensive, (turbo, FAP / additive, differential pressure sensor, solenoid valves, etc, etc). If you change that lot at Pug prices you'd spend more than I did on the car.
Some problems, (I discovered), are down to a little vacuum actuator that works a set of throttle butterflies, which regulate the intake airflow. This can fail for a variety of reasons - the test is simply to observe it move while working the accelerator from under the bonnet.....
Took ages to find mine, but I eventually found it on the gearbox end of the head and Eureka! the linkage has snapped off!
My initial euphoria at finding the problem has now abated a little, because:
a). Limp mode didn't happen again after getting to work.
b). The fault has cleared itself without me fixing the actuator.
c). How would it know this was broken in the first place?
d). According to ServicePox, this'll rush me £18.94 for the complete actuator, when its only the plastic rod end bearing thingy that's broke, (which is probably worth about 4p)

Guess I should still count myself lucky, but if anyone has an alternative suggestion for replacing the offending bit, (part of item 12 below), please do tell. Scrappy's the obvious answer, but not many 2.2 Hdi's to be found.
