Turbo underboost! Help

[baldybouncer]

Bought van with issues - replaced turbo,intercooler and N75 valve - still not boosting and throwing fault code.

Checked pipes and can't see anything - DPF is about 20g I think

Any suggesions?!

[Doc]

Which engine?
Do you have VCDS to carry out some diagnostics testing?

[baldybouncer]

Only got Carista - I can see the turbo is producing about 1/4 of the required boost -

[baldybouncer]

Sorry mis-read

The van is 2011 1.6tdi CR - I bought it after being told the turbo needed a replacement... replaced turbo with reconditioned unit ( no change ) replaced turbo control valve ( no change ) replaced intercooler ( had holes in it! - no real change)

My mechanic friend is in bed with covid and really need to get the van running properly for work

[SRAutoSolutions]

Everything you have mentioned can be tested before replacing parts.

do you have a vacuum gauge or mityvac? does your diag equipment have live data streams?

[baldybouncer]

I don't no- I have carista that is showing the turbo expected and actual are way off. You can see the boost isn't getting to the engine.

I have double checked all vac hose and can't find any splits etc. I am thinking maybe the EGR could be the issue?

A friend who is a mechanic has covid and can't obviously look over the van at the moment.

Anything else I can check?

[baldybouncer]

Does the actuator need adjusting or setting up? The turbo was a recon unit so the original....

[SRAutoSolutions]

I don't no- I have carista that is showing the turbo expected and actual are way off. You can see the boost isn't getting to the engine.

I have double checked all vac hose and can't find any splits etc. I am thinking maybe the EGR could be the issue?

EGR jamming open can cause a major boost leak. This is where live data comes in handy, there should be readings on there to tell you its position. (and testing options depending on diag equipment.) other option is to blank it off.

if the turbo is vacuum controlled find a bit of pipe to fit onto the actuator (4mm internal diameter i think) and with the engine running sook it you should see that actuator moving and should see the pipes hardening up with pressure. sook to fully moved and clamp/fold the pipe to keep the vacuum which will test the diaphragm (if it starts to creep back in diaphragm fault).

is there any fault codes?

if the intercooler had holes, how are the boost pipes? all vacuum hoses definitely going to the correct place? The actuators should be marked.

[baldybouncer]

The issue - was a leaking rocker cover! The rocker holds a vacuum reservoir and due to leaking didn't work.

I fitted a vacuum reservoir from a mk5 golf in the pipe and its now prefect!

Thanks for the help - just need to sort gearbox out now!

[Ivorytoast]

The issue - was a leaking rocker cover! The rocker holds a vacuum reservoir and due to leaking didn't work.

I fitted a vacuum reservoir from a mk5 golf in the pipe and its now prefect!

Thanks for the help - just need to sort gearbox out now!

Hi mate, can you give me more info on the vac reservoir in the pipe you fitted please. I think I have the same prob

[Atomizer31]

Hi, I have similar issue. Is there a good aftermarket replacement for the whole Boost setup, flexible and rigid hoses, Inter-cooler. I've already replaces most of the hoses and still can't resolve the issue.

[parrilha]

I suspect Darkside have them but you could just take the van to someone that works with inox to build you some pipes, if done properly the results are amazing!

[gazwilson]

2014 Caddy 1,6 - 96000 miles.
I Just thought I'd post my findings after my long frustrating hunt for an underboost issue and consequent limp mode repeating on my sons Caddy, hopefully it might help somebody.
I used my VCDS to check out all kinds of parameters and went through replacing hoses trying to find the leak. I thought I had found it on several occasions, especially after replacing n75, only to be deflated some days later by the dreaded limp mode.

I had already removed the MAF sensor and cleaned it and it was giving good values on VCDS and similarly removed and cleaned the oil from the MAP sensor. Just for thoroughness I added a tiny bit of silicone grease to the MAP sensor o-ring to ensure the MAP sensor went back in smoothly. This lasted a couple of weeks before limp mode returned. I removed the MAP sensor again as I had noticed the o-ring looked a little worn but didn't have a spare to replace it previously.
I then found in my spares kit an old MAP sensor from my old Audi and the green o-ring was the same. Swapped it over and it was clear that the one I was replacing was ever so slightly worn but not really obvious without close scrutiny.
We have had no limp mode now for 6 weeks, fingers crossed I haven't jinxed myself but I think there must have been a very slight leak past this o-ring that was causing our issue. I'm not sure where the o-rings can be bought from but this may save somebody the additional expense of replacing the whole MAP sensor.
Possibly worth a try
Good luck

[PeterAFox]

Everything you have mentioned can be tested before replacing parts.

do you have a vacuum gauge or mityvac? does your diag equipment have live data streams?

Yes.
Do a graph of the expected and actual boost - VCDS does this, I don't know about your diagnostic tool.
Probably the best place to start - 'diagnosis' rather than 'poke, change parts and hope' is 95% of the time cheaper and quicker (and causes less damage) unless one is a really experienced mechanic

[gazwilson]

Just an update on my previous post. 1000 miles on and no limp mode so hopefully the o ring replacement might be a fix.