Boost pressure reading too low > goes to limp mode

[Superflan]

Hi,

wife's Renault Koleos, a common-rail turbo-diesel Powered SUV (4WD, CVT) got mad in my hands.

I spotted something strange about 2 weeks ago. I was driving, uphill, pedal-to-the-metal. Something between 3000-3500rpm there was loss of power (cut). Back to normal when I let rpms come back to more decent readings.

I thought "OK, I'll look into it when I got some spare time for that".

2 days ago, got on to the "highway", pedal to the floor to get in... Power cut... I didn't release the pedal quickly that time. It triggered the limp mode.

This morning I went to the dealer to read error codes and get out of limp mode, if possible, while waiting to fix it.

Quote:
Things were going like this at the very moment that the freeze frame was shot:
Wrong boost pressure. Read 2bar, should've been 2.5bar


So, what do you think guys ?

-boost pressure sensor ?
-variable geometry stuck ?

Maybe the problem is here for quite some time, because we barely drive it above 3000rpms, so was unseen till now. It's a car that is driven start-and-stop (approx. 60 per day) half of the time, so maybe it's quite full of gunk in the intake runners, EGR, and so on. But no DPF problem for now.

I'm out of limp mode now.

 

[Kamele0N]

common issues on turbos...

broken membrane on turbo....vw refers on this as N75 valve...

On service they will say that turbo is broken and they must replace it (700-1200eur issue)

but you have to only replace "that" pressure valve....for +/- 100 eur...

 

[Superflan]

Wastegate you mean ?

 

[Kamele0N]

Yeah.....in my language we refer on that as "pressure valve" or something...

Membrane inside that actuator...wich controls opening and closing of the turbo.

Check that first before you/service replace turbo.

 

[The_Eric]

Not knowing anything about your ride, I'd second checking the waste gate and it's actuator too.

 

[Superflan]

Thanks all, I will look into it. Should buy a diag tool before road testing the repairs because going to the dealer is now my only way to get out of limp mode, if it falls in it again.

Will get a CAN CLIP to stay away from the dealer, even if it costs a lot, we plan to keep that car as long as possible, so maintenance will be done at home if possible.

I'll keep you updated !

 

[Kamele0N]

Open the hood.....start engine.....say to somebody to "pump" gas pedal to various rpms.....and check actuator if its moving...

 

[Superflan]

Boost pressure can't build up to the value it should, the wastegate should be opening too early then ?

I don't think it will move that much if there isn't load?

Plus it's fly-by-wire throttle.

I'm not into turbo mechanics, thanks y'all to teach me wastegate haha !

 

[HerrStig]

Originally Posted By: Superflan
Boost pressure can't build up to the value it should, the wastegate should be opening too early then ?

I don't think it will move that much if there isn't load?

Plus it's fly-by-wire throttle.

I'm not into turbo mechanics, thanks y'all to teach me wastegate haha !
Will all due respect to where you live, it would be the place for a very simple diesel vehicle, I would think. I've never been there, but I think I've talked to just about every ham radio operator on the Island.

 

[Kamele0N]

French car + diesel engine, just best combination for....that island! ( I am missing smiley with devil!)

 

[Jetronic]

I'd expect a VNT turbo in that car, so no wastegate...

And I question the low boost triggering limp mode, it's high boost usually that does this.

 

[Kamele0N]

Actuator is again "in game"

Or could be that is variable fan wich is stuck...

 

[Jetronic]

yes, but the symptoms will not be the same.

 

[Kamele0N]

That guy had same problem on Audi 1,9TDI.....safe mode because stuck rotor...

here is his DIY (pictures)

http://www.alter.si/tabla/showflat.php?C...e=0&fpart=1

 

[Superflan]

Turbo is a GARRETT GTA1549LV, OE on some Nissans (Qashqai) and Renaults.

After looking at it and comparing to pictures found on Internet, I understand the basics of classic wastegate command and pneumatic VNT command (my case).

I tried to get the actuator moving by throttling on neutral, but can't see anything move.

I see that the pneumatic actuator is connected to a solenoid valve, I will remove it from the engine bay and blow in it, with and without voltage applied, to see what's going in (and out ).
I can see this part is cheap (less than EUR 50) and available on every Internet car parts stores, so I assume it's a common thing to fail.

 

[Jetronic]

be carefull, the solenoid might not take kindly to 12v applied directly.

 

[Superflan]

Update: i was juste having problems of paper panel air filter getting wet and then being restrictive. Bad filter design.

 

[Superflan]

Update: no more problems after switching to another filter brand and changing air filter each oil change

 

[DoubleWasp]

If I were you, I would install an air filter restriction gauge to prevent that from happening again.

 

[Superflan]

Thanks for the advice. Never seen one IRL. How does it works ? (FilterMinder ?)