It looks like the same part, but it doesn't function like a petrol throttle body.

Diesels take a full air charge all the time, there's no need for a throttle plate to restrict air at lower fuel amounts, like there is on a petrol.  The throttle pedal has no effect on this valve in a diesel.  You can even unplug this valve and the engine will still run perfectly well.

They're fitted for 2 reasons.  One is to close off the intake completely when you switch the engine off to stop the stutter/clatter that you'll get without it.  But the main reason for it is to work with the EGR valve.  When the EGR valve opens, airflow dynamics dictate that not all the recirculated air gets pulled away from the exhaust. If you introduce an intake restriction, then the engine has to pull all of the recirculated gas as it can't get a full charge from the intake air alone.

Hopefully that makes sense!

Its certainly plausible that there's a fault with yours...and for the sake of £30 for a used one, I'd just replace it rather than faff around any longer with live data readings lol.

I will try a replacement in that case, but question is does the ecu need to learn the new valve, do I need to do anything other than just change it?

13 hours ago, Ionise said:

I will try a replacement in that case, but question is does the ecu need to learn the new valve, do I need to do anything other than just change it?

I can't remember unfortunately.  If there is a relearn procedure, it'll be in Forscan.  

I think you'll get away with just fitting another though.

One on order will be sure to let you know the outcome, pretty sure there was no learn on forscan for the throttle

Thanks

It's been a while, I should have updated sooner.

So, Air intake throttle replaced like for like (2 months ago), straight after changing I fired up the car went for 15 min drive power was the same (low).

The day after I noticed the power was almost back to normal, since it has not had low power like it had been, BUT occasionally the power goes high (like it has been doing, I measured 0-60 in 9 seconds, bare in mind the car is 11 years old and should only be able to do it in 10-11s from new). Power when it goes high lasts 10-15 minutes usually and sometimes happens a few days in succession, sometimes just once a week, very random.

When the power does go high, if I park and leave the car idle, the MAP pressure is 70kpa (same as previous when power came back). MAP could only really pull a vacuum if the air intake throttle closed too much right? Why would it close too much, and why whatever cause this cause high power - so confused. 

 

Did you ever figure out the problem im in the same boat ive replaced the egr . Still no good help