I noticed that the turbo actuator was moving about all the time while the engine was idling.
Looking at the ODB logs, the drive to the actuator, VGTDC was not moving much. However the MAP was ramping up and down every 10 seconds. This matched exactly the movements in the actuator.
My theory was that there was a vacuum leak which allowed the actuator to gradually sink back. The ECU applies a puff of vacuum every 10 seconds and this makes the actuator jump back again.
Well today I tested the boost control actuator.
I attached a pipe to the vacuum actuator on the turbo and stuck a syringe on the other end. Pulling the syringe creates a vacuum and the actuator moves and stays put.
So it works fine and hold vacuum.
I then went looking for the control solenoid. Some people call this the boost control solenoid but the supplier and Ford call it a Pressure Converter Valve.
It located behind the engine on the drivers side, low down, just above the steering rack.
See pic.
To get to it, you need to take the under cover off (6 or 8 screws). then get right under the car and look up past the steering rack. The valve has a 2 wire connector and 3 pipes on it.
The pipes are from the left, vent (to the small air filter on the end of a pipe at the back of the engine bay, just under the wipers), vacuum out to the actuator and vacuum in from the vacuum pump via a reservoir.
It's easy to get off once you get access to it.
I made a fork shaped pipe puller to avoid damage to the rubber pipes. It slips over the tube and pulls the rubber hose off.
I tested the valve with a syringe and some pipe and it leaked air.
So I bought a new valve. Ford charge £125 for these. They are on ebay for £45 but I decided to go with Eurocarparts (and get a warranty). It was £64, but I had to buy one for a Citroen as they didn't list the Ford one! The valve is the same and it's made by Pierburg part code 7.00968.03
Yoyo parts shows all the car part codes for it.
http://www.yoyopart.com/oem/5609465/...-70096803.html
So I stuck the new valve on and hey presto, no more turbo actuator movement on idle and no MAP changes when idling.
Out on the road I have full boost in all gears and the car goes like a rocket!
So before getting your turbo replaced, check what the MAP is doing on idle and what the actuator is doing too.