2007 Audi A4 2.0 tdi 170bhp Booster pressure not working (vacuum on manifold not working).

Audi A4 Problem
The Problem
Fixes: 3
Booster pressure not working (vacuum on manifold not working).
May 6, 2013 (7 years ago)
The booster pressure is not working. I have changed all the parts and the vacuum manifold flap but it's still not working. Any ideas why the air is not being sucked in when the engine is being revved?

Car details
Car: Audi A4
Variant: 2.0 tdi 170bhp
Model Year: 2007
Category: Engine & Drivetrain

Recalls: Audi A4 Recalls
More: Audi A4 Problems
Replies and solutions
Fixes: 1,862
May 7, 2013 (7 years ago)
nes by their very design don not produce vacuum at the manifold like petrol cars do.
Mostly diesel engines use the vacuum pump that serves the brake booster servo,some of the vacuum is directed to the turbo boost circuit,then to servo pressure switches.
Start by making sure you actually have brake vacuum from the pump,
easy test is the booster test.
engine off,pump the brake pedal 4 or 5 times then hold it down as far a foot pressure can maintain,then while hoding pressure key on and start the engine,the pedal should dip lower under your foot,
no dip means no servo pressure.
Next test would be a vacuum gauge on the line from the vacuum pump when the engine is running,then it's a case of following the vacuum down to the pressure sensors/switch then the turbo dump valve.
Fixes: 3
May 18, 2013 (7 years ago)
hi I get audi a4 170 bhp some times the rpm goes to 1000rpm when my foot is not on the pedal any idea's what is wrong? thankyou
Fixes: 3
May 18, 2013 (7 years ago)
Have you had a look at this similar problem:

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