Strange Maf fault ..help please..
 

2010 XC90 D5 210,000 km.

I have a strange MAF fault ECM-134f When I start the car I get the Engine service message and the fault codes appear in Vida , the car runs poorly and has no power . When I clear the fault codes the car runs normally I took it out for a hour yesterday on the motorway and up hills and it ran well. The odd thing is if I turn the car off even for up to 1 hour it starts without the faults . But if I leave it for a couple of hours or longer the faults return and I need to clear the codes before I can drive it normally . I have attached images of the sensor readings at different engine speeds and with and without the fault being cleared .
In trying to fix the fault I have cleaned out the intake pipe and the throttle body and changed the resonator pipe for a silicon one.

Thanks

When you single click on a value in ECM >Parameters then click on description for a full list of the figures they should be.

The MAF data looks credible so I doubt that it's a problem with the actual sensor and nothing is screaming out as being wildly wrong in the data so far.

I would also be checking and comparing:

Intake manifold pressure
Boost pressure
Boost pressure actuator pwm
Intake air temperature

Additionally, check the swirl arm is attached and moves correctly in ECM >Activations and that you can hear the EGR clicking open and closed in ECM >Activations.
Do these activations with ignition on only.

Todays update , Cleaned contacts on connectors on Maf and egr , removed and cleaned the ground wires that are next to the fuse box.

Checked different activations all good , did reset on Maf .

Still no luck , I made 2 graphs as you can see the car runs normally when the fault has been cleared , but no turbo when the fault is displayed.

sorry about the poor images .

The key to your problem may be the fact that its ok when hot but comes back when cold ,,, maybe the turbocharger control vanes are sticking ....

Just to be clear the fault always appears when the car has been sitting for over a hour , the dashboard warning comes on as soon as I put the ignition on position 2 and before I have started the car . The car runs great once the code has been cleared and no faults appear until the car is restarted later.

Turbo vanes sounds expensive , is there a way I can check with vida if thats the problem ?
I just did a quick google and saw that you can buy turbo cleaner sprays that you spray down the air inlet after the Maf . no idea if it would work.

https://www.amazon.co.uk/gp/product/...9ca87025d048e5

have you compared the air pressure from the 2 ( or 3 *) atmospheric air pressure sensors with just the ignition on ? they should all be very close at the barometric pressure where the car is ... in recent years the one in the intercooler outlet pipe can sometimes give a slightly incorrect reading ..

The Atmospheric sensor in the ECM is the most reliable reading to take as true ...

*= some models have a third atmospheric air pressure sensor in the inlet manifold

Thanks, they appear to be similar , I am bit stumped as Volvos are not very common where I live , the local main dealer is just a add on to other car franchises with only 1 Volvo mechanic and from what I have been told keeps putting on new parts until he fixes it (or not).

That must be a "Volvo authorised Repairer" rather than a dealer ... if they are legitimate they don't work like that ...

is there a boost sensor in the intercooler outlet pipe by the side of the radiator down low on the passenger side?

Hi Clan , I think you hit the nail on the head regarding the sticking turbo blades , I decided to try a cleaner I used a liqui moly diesel intake cleaner

https://www.liquimoly.com.au/3029-di...ke-decarb-326g.

I put the tube in the intake pipe just after the maf and used small 1-2 sec bursts and leaving 5-10 second gaps , after that I took the car for a 30 min easy drive and then gave the turbo a bit of a spin on the way back.

That was 12 hours ago and the car is still starting with no fault codes and running fine .

Only time will tell if its fixed or not.

Thanks for your help.

Good one , the vanes were probably sooted up then ...