C30 D5 2008 - Low/down on power

[PCW8256]

Hi,

Hoping you can help with my weird D5 issue.

A couple of months ago, I noted an error to do with the exhaust differential pressure sensor which had incorrect values.
I had a look for it in the engine bay and proceeded to remove and put it back on.

After doing this, the car was noticeably quicker, as in it really felt like a rocket and drove fantastically. MPG was good also.
The error still was present so I thought I'd better replace it.

I replaced it with a second hand low mileage sensor and the fault code disappeared after calibrating the car with the new sensor.

The issue now however about a month after having a great performing car with decent fuel economy, I seem to be back to square one but with no fault codes.
The car feels sluggish and down on power once again and honestly I don't know where to start as everything appears normal...?

Any known issues on these vehicles?

[Rossco1962]

Hi you haven't said what mileage the car is and does it do a lot of slow around town trips as opposed to a Spirited drive on the Motorway.

If you look under the bonnet is there any signs of black soot covering the engine and bonnet as this could indicate a blocking of the DPF. When you drive it with the window down does it sound like it has an exhaust farty sound when accelerating.

Other area's to check include:

Vacuum leak , split in the induction side or leak. Blocked MAP sensor are just a few of the causes but without getting the system scanned with DICE its very hard to tell.

I've had fairly similar faults on my 1.6d and hence changed the MAP, DPF and Turbo and repaired a leak in the hose from the intercooler and also a vacuum leak to the turbo actuator together with topping up the PAT fluid and resetting the anti pollution service interval and the car runs a lot better but still occassionly throws up a fault code.

This might sound bonkers but how old is the battery. I had a gold that would through up a fault code and go to limp mode on a daily basis despite a 90 mile round trip at 50 + mph. I declined the offer of a garage to keep changing items related the throttle position sensor fault code and came out 1 day to find the car dead. I replaced the battery for a good second hand item and the fault never appeared again

Good luck

[Simmy]

Originally Posted by PCW8256

Hi,

Hoping you can help with my weird D5 issue.

A couple of months ago, I noted an error to do with the exhaust differential pressure sensor which had incorrect values.
I had a look for it in the engine bay and proceeded to remove and put it back on.

After doing this, the car was noticeably quicker, as in it really felt like a rocket and drove fantastically. MPG was good also.
The error still was present so I thought I'd better replace it.

I replaced it with a second hand low mileage sensor and the fault code disappeared after calibrating the car with the new sensor.

The issue now however about a month after having a great performing car with decent fuel economy, I seem to be back to square one but with no fault codes.
The car feels sluggish and down on power once again and honestly I don't know where to start as everything appears normal...?

Any known issues on these vehicles?

if you continue to drive with dpf problems it can throw up a tcm code which gives reduced performance

[PCW8256]

Apologies, I didn't give a great deal of information.

Car has done approximately 105k miles so not exactly a high miler.
Whilst it does do a fair bit of round town trips, it doesn't pick up on long journeys. I would put this down to a DPF issue, however looking at VIDA the soot level in the DPF is very low.

No codes logged now and no obvious signs of fault in VIDA.

My first thought was vacuum however there doesn't seem to be much of a vacuum system to look at apart from the brake booster (unless I am missing something obvious).
Boost is controlled electronically and I've even checked the free movement of the turbo vanes.

Boost and intake pipes are spotless and honestly the engine is one of the cleanest I have seen so it's a complete mystery....

[INS60T]

Have you tried disconnecting the MAF or via VIDA (I assume you can) check the values the MAF is sending?
Of course it may be something entirely different, but from the symptoms described it reads a lot like a MAF that's on the way out or maybe needing cleaned.
What sort of air filter are you running?

[PCW8256]

Hi no I haven't checked the MAF. I've never had a MAF go. I could look at that next. I am not sure what value I would be looking at.
Again, the engine is spotless so I would be surprised.

Standard air filter is fitted pretty much new.

[INS60T]

Don't worry about the VIDA figures, just take the car for a lock down shopping run with the MAF connected, on the return disconnect the MAF. If the car runs better.... it's most likely the MAF.

Albeit not on a Volvo I've either changed or cleaned MAFs almost as a service item on Alfas, Fiats, a couple of VAG cars and a Ford for either myself or friends. All the cars displayed symptoms like the ones you describe - so the MAF test is worth a 'punt', even just to exclude it as an issue.

If the car runs better with the MAF disconnected, before replacing the MAF you could try cleaning it with electrical contact cleaner which is what I used.

[PCW8256]

I finally tried the car without the MAF and unfortunately the power was way way down without it so clearly it's working fine.

I am so out of ideas it baffles me on what to try next.