So this seems to be the never ending turbo underboost issue. Under heavy load it does this and its rectified with a simple ignition on/off. I had initially thought it was the vacuum block, but I've tried a couple of different ones now and we're still getting the fault (hoping the 2nd hand ones aren't faulty). Tried doing some research and saw some have a boost control solenoid, a faulty one would absolutely make sense. I've searched the engine bay and nothing found. I assume I don't have one, there's only 2 vacuum pipes to the turbo, both leading back to the aforementioned vacuum block and shown in the photo.

Is it likely I've been unlucky with the 2nd hand parts or am I barking up the wrong tree? 

 

Cheers for your thoughts 

 

Ben

 

Check cabin fuse 24.

Barking up the wrong tree.

 

No boost control solenoid on the Mark 1.

 

Please post the DTC relating to underboost.

Edited 9 June, 20214 yr by sepulchrave

N75 Charge pressure control solenoid valve is one of the three solenoid valves inside the 'vacuum block'.

Fuse 24 supplies all three.

Boost control solenoid means an electronic actuator like those fitted to the mark 2, not a PWM vacuum bleed solenoid, obviously.

 

 

 

Can you tell me which mk2 engine code(s) use(s) such a thing so I can learn about the 'obvious' difference, please?

Easier just to show you the thing:

 

https://www.darksidedevelopments.co.uk/products/electronic-vacuum-actuator-for-1-2-tdi-cr-engines.html?gclid=Cj0KCQjwzYGGBhCTARIsAHdMTQxHLCjP8fjhftE0oR0-r4Qm2KeRESCHJ_6UGZD4lNOMDj7WKCMQtNcaApHeEALw_wcB

Cheers. So just merging the solenoid valve into the vacuum motor, by the looks of it?

I think it has positional feedback as well.

1 hour ago, Wino said:

N75 Charge pressure control solenoid valve is one of the three solenoid valves inside the 'vacuum block'.

Fuse 24 supplies all three.

Thank you, checked and all good. 

1 hour ago, sepulchrave said:

Barking up the wrong tree.

 

No boost control solenoid on the Mark 1.

 

Please post the DTC relating to underboost.

Code p0299 turbo underboost. 

On this appearing it goes in to limp mode, remedied with an ignition flick off/on. Only happens under high load i.e hard acceleration or inclines 

10 minutes ago, Bengunn007 said:

Code p0299 turbo underboost. 

On this appearing it goes in to limp mode, remedied with an ignition flick off/on. Only happens under high load i.e hard acceleration or inclines 

 

http://wiki.ross-tech.com/wiki/index.php/16683/P0299/000665

 

Pay particular attention to the very last paragraph.

14 minutes ago, sepulchrave said:

 

http://wiki.ross-tech.com/wiki/index.php/16683/P0299/000665

 

Pay particular attention to the very last paragraph.

Thank you. Are you suggesting the vacuum hoses could have a leak only presenting itself under higher vacuum induced loads? I've visibly checked the relevant hoses with nothing obviously damaged.

You need to use a gauge to test for vacuum loss.

18 minutes ago, sepulchrave said:

You need to use a gauge to test for vacuum loss.

A generic gunson/sealey vacuum tester good enough for this?

On 09/06/2021 at 22:00, sepulchrave said:

You need to use a gauge to test for vacuum loss.

The vacuum pipe to the actuator seems to be able to hold vacuum indefinitely. Would thus suggest it's the n75 within the solenoid block and I've just managed to get another one with an issue?

You need to check the entire vacuum system for leaks, not just the actuator line.

7 minutes ago, sepulchrave said:

You need to check the entire vacuum system for leaks, not just the actuator line.

I can check the opposite direction in to the solenoid block, should that hold vacuum just the same? Anywhere else to check from there? Apologies for all the Qs no experience fault finding in this manner at all. 

Thanks Sepulchrave

Check the vacuum starting at the pump, not the N75 block.

3 hours ago, sepulchrave said:

Check the vacuum starting at the pump, not the N75 block.

Really hoping this is the culprit!

Thanks for your help!

Wow, that really won't be helping matters!

5 minutes ago, sepulchrave said:

Wow, that really won't be helping matters!

So that's the vacuum pump to brake booster pipe. But it's just after the T-pice that goes to the solenoid block. It wasn't quite so bad until I went in for a closer look so I'm hopeful this has been the toot cause. Now just to find a replacement 🙄

7 minutes ago, Bengunn007 said:

So that's the vacuum pump to brake booster pipe. But it's just after the T-pice that goes to the solenoid block. It wasn't quite so bad until I went in for a closer look so I'm hopeful this has been the toot cause. Now just to find a replacement 🙄

 

You might be able to cut the split part off, heat the pipe until soft and push it back over the barb whereupon it will harden and set in place.

5 minutes ago, sepulchrave said:

 

You might be able to cut the split part off, heat the pipe until soft and push it back over the barb whereupon it will harden and set in place.

I'll give that a go, even if it'll see me right until I can source the correct replacement. Thanks

Nice crack!