I have an Audi A3 1.9TDI 110ps (direct injection diesel – NOT PD), and I’ve been having turbo loss problems for the last 6months, intermittently. I’m getting fault code 17964 (charge pressure loss). I started off by replacing some of the vac lines which looked frayed – the problem went away and then came back. The problem comes and goes – for weeks the turbo will work fine, and then the fault returns, then the fault stops happening etc etc.

2 Weeks ago the problem was back, and I also noticed the brakes were not working right either. I checked the brake servo hose (this was fine – only replaced 12months ago) and found the vac line which plugs on to the brake servo vac hose, near the vac pump (on the end of the cylinder head) had come unplugged plus one of the vac lines to the idle control valve (N239) was unplugged. Plugged these back on, and performance was back to being normal, plus brakes now ok. Then a week later the problem of turbo loss is back! So I then replaced ALL vac lines with silicone rubber hose – the car/turbo then worked fantastic > turbo kicking in at 1800revs.

And now 5 days later the turbo loss is back again, and I’m at a loss…..

Typical scenario is accelerating though 3 rd /4 th /5 th , and in 5 th at 2400 revs the turbo cuts out.

Switching off/on clears the problem (until it returns).

It does it with/without the Air Mass Meter plugged in.

And the odd bit –

When I disconnect the vac line to the turbo actuator, and suck, I can’t feel the actuator rod move. However, if the diaphragm was split, surely the turbo would never work? The actuator wouldn’t move when I sucked on it, immediately after replacing all the hoses with silicone pipe, yet when I took the car out, for the first time, the turbo worked great. Plus when I suck on the vac line, I can hear air being sucked in around the area of the N18 solenoid valve. At least I think it’s coming from area – but it makes no sense!