V50 Engine 2.0D : Oscillating power at full throttle

[Bikeman]

Hello all,

I've tried to search this forum for posts describing a problem similar to mine, but after reading the first 10-some pages of topics, I thought registering and starting a thread myself would be more efficient. So here I go ...

Since one week I own a second hand 2005 V50 2.0d, mileage about 85k miles (live in Belgium, so it's 138500 km). Very nice car for as far as I can tell now, but there is one main problem.

When driving in fourth gear or higher, running the engine at moderate rpm's (1800 rpm) and then going to full throttle, the motor seems to hesitate to give it's full power. The first two seconds torque builds up nicely, then it goes down for a second, then back to full torque for about two seconds, then goes down again and so on(but by that time I'm driving too fast so quit playing that game).

I've read a lot about EGR valves, about pressure sensors measuring the state of filters, about failing turbo's, but I've never found the exact symptoms I have mentioned explicitly, so I was hoping some of the experts here can pinpoint the cause of this behaviour.

Thanks in advance!

[Guru]

Hi Bikeman, welcome to the forums and congrats on your purchase a number of things can cause hesitations and power drops...

If you hadn't mentioned fourth gear i would have assumed that you have a faulty throttle body/accelerator pedal sensor, the accelerator is electronic and works like a potentiometer... but a faulty pedal modul would cause hesitations through out the gears and not just after accelerating from 4th.

Another thing that could be faulty is the TCV "Turbo Control Valve" encircled in yellow in the pic, you'll have to take it in for investigation, not quite sure whether it has diagnostics, but surely Volvo or an experienced car electrition would know how to test its functionality.

Many other things come to mind, i.e. a clogged air filter, faulty MAF sensor, disconnected InterCooler hose, or IC full of soot, hope it's not a failing fuel injector or fuel pump, have you had your fuel filter changed?...

Am afraid there are so many possible causes, so you'll have to investigate systematically, excluding as you go so start with the basics, if you have a clean AF then try disconnecting the MAF, then go for a drive, if it makes no difference then you have a winner, if not; inspect the front IC pipes by pulling off the black fog light plastic covers, use a bright flashlight to see through the tunnels...ect.

And at the end it just might be that EGR valve.

[Clan]

its classic symptoms of the turbo boost valve as above .. get the repair kit from the dealer it consists of a bracket pipes and valve for just £50 a bargain .. fit the pipes too as they could be partialy blocked .. the bracket cracks so fit that too . or the valve will fall off and jam the gear change linkage !

[Bikeman]

Thanks for the replies!

Searching the internet for the turbo control valve and what it does exactly didn't really come up with many matches. Is it the waste gate of the turbo, or is it another turbo-related valve?

Anyway, I'll go to a dealer next week and have it checked out. I'm glad I have a little background now!

[Guru]

Should be OE number 30650769

[Clan]

Originally Posted by Guru

Should be OE number 30650769

That could be £114 as the D5 one is and it is the same part ..
The repair kit with bracket contains bracket , pipes and Valve for £50 .

[2.4TSE]

Yup, absolutely perfect symptom of the Boost Control Solenoid failing. I live in the UK, but mine failed in the Czech Republic and I drove all the way home with GO-nothing-GO-nothing-GO... Drove me mad! If only I had known the cure to be so simple...

[Guru]

Originally Posted by Clan

That could be £114 as the D5 one is and it is the same part ..
The repair kit with bracket contains bracket , pipes and Valve for £50 .

50quid is quite a good price if it's the same valve, do all dealers sell these repair kits? coz I think Bikeman is from Belgium...

[Clan]

didnt realise he was from belgium , it may be just a UK thing ..

[Bikeman]

I just went to the procedure to check for any set error flags in the car electronics, as described in this recent thread: link.

There are quite a few unexpected 'errors': BCM, SWM and ICM are 'CHECKING', EPS, CEM, DDM and PDM give 'DTC SET'. SRS and DIM are ready (despite the fact that DIM doesn't appear on Guru's list in the thread above). Hope these things aren't all too bad, because this makes me feel like I've bought an electronic wreck of a car ...

But surprisingly the ECM (Engine Control Module) apparently has no error flag set. It says 'ready' ... Could it be that the control valve is failing without the electronics knowing about it?

I've also checked the valve that is indicated in the photo above. It's easily reachable, so I hope that having it serviced by the dealer won't cost me too many additional euros ...

EDIT: Fuel consumption is very reasonable, by the way, averaging 50 MPG the two tanks I've driven it. Highways, mostly, at a decent 80 mph ...