Hi all I’m new here I’ve recently bought a mk2.5 2009 Focus estate with the 2.0D TDCI engine in runs a dream has recently developed a fault of a slight judder on idle and when I turn the engine off it’s really harsh doesn’t shut down like it should. looked into it and found my anti shudder/ air shut off flap isn’t getting any vacuum, checked all the vacuum to the solenoid on top of the A/C pump that’s all there voltages are all there but it wasn’t outputting vacuum on shut down of engine or occasionally at idle like it’s supposed to. Replaced the solenoid as I thought it was at fault but still the same, Have seen a couple of threads on here people with the same fault no vacuum coming from the solenoid to the flap but no one has mentioned if they’ve fixed it just wondering if anyone has or if anyone knows of the fix 👍🏻

12 minutes ago, Gizmo30 said:

checked all the vacuum to the solenoid on top of the A/C pump that’s all there voltages are all there

First check that the throttle valve is not jammed, and if it is now getting vacuum. It is possible that the solenoid & throttle were both faulty.

When checking for voltage at the solenoid, you need to do this with the solenoid (or a comparable load) is connected. If done with the connector removed, there is no current, and bad connections in the wring will not be reliably revealed. You can use "back probing" to check voltages with the connector on the solenoid, basically sticking sharp pins into the seals at the back of the connector to make contact with the pins, if you have not already done this.

Also it is quite possible for vacuum hoses to develop internal blockages which only become apparent when under vacuum. The inner lining of the hose can detach from the outer, blocking the hose when pulled in by vacuum. I once had a brake servo hose like this, it was fine the 1st time I put the brakes on, but the 2nd or 3rd time in that deceleration (typically on final approach to the junction!), the servo did not work, needing massive force on the pedal, not nice!

Basically it now means going through the chain from vacuum pump to throttle step by step, and don't assume that the replacement solenoid is free of suspicion! Faulty new parts are quite possible.

Thanks for your reply Peter I’ll remove the vacuum pipe and replace it tomorrow, I’ve checked the flap works fine applied vacuum to the vale with a miti vac to check the diaphragm all ok plugged it into the control hose nothing on ignition off didn’t think of replacing the pipe what a dope 🤦🏼‍♂️ Had the problem on clutch flex hose before. If all that’s ok I’ll update didn’t know if the others found their issue 

Just an update on the issue checked all the vacuum lines they’re all ok not collapsed internally, I’ve got vacuum upto the vacuum box on the block then from there to the solenoid have 12v at one pin and 3v at the other a new solenoid but when I ignition off it doesn’t pass the vacuum through the solenoid to shut the flap 🤔 I’ve seen a few posts on here and online about others having the same issue but they don’t update the thread when it’s fixed 🤦🏼‍♂️

4 hours ago, Gizmo30 said:

then from there to the solenoid have 12v at one pin and 3v at the other

9v over the solenoid seems a little odd. I am not sure which way the valve & solenoid work: If it needs vacuum to shut, or vacuum to open, and also if the solenoid has to be energised for vacuum at valve, or de-energised for vacuum. I assume that 9v was with the engine idling, in which case the valve should be fully or partly open. If the solenoid has to be energised for valve open. then it could be right, with the ECU cutting back the power a bit (from 13v to 9v) to avoid overheating the valve.

If the car has a cDPF, the throttle valve should have a position sensor. Forscan should be able to read this sensor, and tell you if the valve was moving at all with the ignition on. It does not work (no diagnostics) with ignition off, so won't directly test the ant-shudder operation, but can still give useful info.

Threads that just end with no conclusion are very, very common, not just on this site, but generally. It can be very frustrating!