ME7 T5 - not enough vacuum hitting 5-7psi on light throttle

[DSK]

I had a routine service and new radiator fitted on Friday. The wrong part being sent cost us over 3 hours meaning the car was put back together and tested quickly just after closing time.

My car is very boost sensitive despite having gates hoses. Anytime anyone fiddles near the vacuum/boost lines or they are disturbed, my car responds differently. The car is running smooth as always, idles fine etc but, at the slightest bit of throttle, it goes to 5-7psi of boost when it's usually still indicating readings below 0psi (vacuum) on the boost gauge.

I've visually checked that the hoses from the TCV are ok, all t junctions are ok etc.

Its going to be about 2 weeks before I can get the car to someone reputable like TW but, would appreciate any suggestions on things to check in the meantime as its sucking my wallet dry on fuel at the moment having dropped 12mpg!

[Clan]

Originally Posted by DSK

I had a routine service and new radiator fitted on Friday. The wrong part being sent cost us over 3 hours meaning the car was put back together and tested quickly just after closing time.

My car is very boost sensitive despite have gates hoses. Anytime anyone fiddles near the vacuum/boost lines or they are disturbed, my car responds differently. The car is runs smooth as always, idles fine etc but, at the slightest bit of throttle, it goes to 5-7psi of boost when it's usually still indicating readings below 0psi (vacuum) on the boost gauge.

I've visually checked that the hoses from the TCV are ok, all t junctions are ok etc.

Its going to be about 2 weeks before I can get the car to someone reputable like TW but, would appreciate any suggestions on things to check in the meantime as its sucking my wallet dry on fuel at the moment having dropped 12mpg!

It seems your boost gauge is connected to the wrong place it should go direct to the inlet manifold .

[DSK]

The boost gauge was fitted by Tim Williams years ago and its always read accurately.

As far as I'm aware the boot/vac lines were not touched but I'll have another root around the inlet manifold area as that is somewhere a line could have been disturbed. I should add that whilst the car is smooth and idles solid etc, there is a noticeable difference in performance. Seems OK low down but definitely slower at the top end since Friday.

[DSK]

Looking down into the engine bay, by the air box, is this TCV the right way up? (showing the blue dot on top).

Whilst looking around again, I noticed it was loose and not clipped into the side of the air box.

[byootox]

So, what are you using to tell you that your getting 5-7 psi of boost.. Vida ?
Have to say I've messed about with the vacuum/boost hoses for the turbo regular on mine and it doesn't make any difference to the performance when I put it back together, no worse or no better.
If your getting differences in power after disconnecting an reconnecting the hoses then I would be concerned of a split in a hose or poorly fitting hose.
If I was curious to the accuracy of the boost gauge I'd try connecting a mityvac to the line and try putting some pressure on it then see if the pressure reading on the mityvac corresponds with boost gauge reading.
Have you checked for any fault codes and live readings ?
Fuel trims in particular if your mpg has dropped so drastically.

[DSK]

I just knocked the hoses around a little bit and its a better and mpg is much better. Its the DEFI boost gauge I use. Historically if there is a problem I spot it by the way the needle moves and knowing how it reacts and where it sits when I am driving. The car is boosting/spooling a lot earlier, you can hear it. Hence why I doubt its the gauge itself.

It may well not be the TCV side and it could be some other pipe/line knocked towards the front of the car as it was put back together in a bit of hurry.

The car is going to TW this weekend and no doubt he'll find the problem and have it sorted in no time. I will report back once done for the knowledge base.

[DSK]

Paid the guru TW a visit and within a couple of minutes the fault was identified via the use of smoke testing.

MAF > Turbo leaking at the PTC and coupling. So this would explain why any fiddling in that area, touching the hoses or changing an air filter would make the car behave differently every time.





1 of the 2, one way valves was not working and a hose near it, by the manifold was also changed.



So in with the new;





The car now drives beyond awesome, the very way in which the silver C70 drove when it was 6 months old is how this C70 feels. A few mm throttle movement results in sublime, smooth whopping increases in speed. WOT is hilarious as well as leaving stuff for dead going up hill even at big speeds. Boost gauge behaviour and readings are now as they should be and fuel consumption is back to being impressive as it used to be.

[ITSv40]

Good to hear it is sorted and the car is back on song.