Hard landing - no error entry - troubleshooting? (Solution)

"I'm experiencing a sudden problem with the shut-off valve. There are no error messages in the control system, the solenoid valve opens correctly when the system is shut down and releases the vacuum to the shut-off valve, but then immediately closes again. The shut-off valve isn't closing completely, as if the vacuum pressure isn't sufficient... The valve can be closed manually by applying suction (at approximately 200 mbar). Everything else is working fine... What's the best way to find leaks? At what pressure should the valve normally close? How long does the solenoid valve need to remain open during the shut-down process?" Vacuum pump?
Stay cheerful.
OlBe.

Hello,

I would suspect a chewed-on vacuum hose, a cracked T-connector, or some other damaged hose fitting.

Simply disconnect the small vacuum hose that branches off from the vacuum pump using a T-connector and connects to the turbocharger control valves and the EGR valve (it's even simpler on non-VTG engines).
Attach a long tube to the T-piece, put it in your mouth, and suck on it.

Now that the engine is off, with a bit of luck, you can hear or feel the leak by gently moving and pressing on the hoses.

You may need to connect the vent hose to the air filter housing, as I don't know how the two solenoid valves will behave when de-energized (it's possible that one of them might be stuck).

Best regards, Rainer.

Okay, I'll start looking for something during the holidays. Perhaps my daughter (4 months old) should come along as a professional vacuum cleaner for leak detection...
Thanks, and all the best.
OlBe.

It was the solenoid valve, located upstream of the pneumatic cylinder that actuates the shut-off valve. It had insufficient flow (no blockage was visible), possibly because it wasn't opening properly. It started to pull, and there was a slight draft that was enough to partially close the flap, but then it stopped, and the valve fell off again.
Valve replaced, engine gently returns to idle...
Stay cheerful.
OlBe.

Hello,

Thank you for the feedback!

Best regards, Rainer.