D5252 Volvo V70 with no power before boost and overall slow
 

Hi!
I have a problem with my Volvo V70 2.5 TDI 2001. I have had this problem for the last two years, but i can't for the life of me find what's causing this :(
The car is running poorly before the boost hits, but takes off (kinda) when it hits. If I'm in 5th gear and pedal to the floor it can take 12-15 seconds to get from 70 to 80 km/h on a relatively flat road.

The boost comes on at around 2000rpm. And boost pressure at full boost is 1bar. I do hear a sound from the engine when i rev it to around 3krpm. It's hard to describe but it sound like a clapping sound. Could this be the injectors?


I've checked for codes but there is nothing. Timed the injection pump and that is OK. With the MAF disconnected it will not go into boost at all, so i will say that it's ok.


- Took off the inlet manifold and burned it clean. The EGR was OK and is functioning (no difference with it blocked off either).
- Tried Liqui Moly Diesel purge and a new filter, without any difference.
- No exhaust leaks.
- MAP sensor reads pressure fine.
- No blown fuses.
- TCV solenoid is functioning as it should
- All vacuum hoses are connected correctly
- No vacuum leaks and no pinched hoses.
- No boost leaks either.

The car always starts without any problems. A little puff of blue smoke on cold start, but I think thats reasonable for a car with 436 000km on the clock.

The car gets an oil change every 10 000km with Castrol 5W-30 and a Mahle filter.

I have some videos that may mean something for some of you.
4th gear pull from around 50km/h, gauge on inlet pipe:

+ YouTube Video

Pull in 3rd and 4th gear with gauge connected to WG:

+ YouTube Video

Pedal to the floor in 4th gear slight uphill:

+ YouTube Video

Pedal to the floor in 5th gear slightly less uphill than previous video:

+ YouTube Video

This is a pull in 5th gear. Red line is boost pressure.
https://i.ibb.co/gT3zC9t/5-gir-pull-og-motorbrems.jpg

Any tips on how i can restore the power in my trusty Volvo would be appreciated!

If you need some more info I will provide it asap
Thanks!

Today i have followed VIDA's instructions to check that the TCV valve and wastegate is functioning properly.

I connected a boost gauge inline with the MAP sensor, and disconnected the line to the WG actuator.

On WOT in 3rd gear i saw 0,45-0,5 bar of boost, wich according to VIDA is where it should be. If the bost is below 0.5 bar the valve is stuck in open position. If the boost is over 0,5 bar the valve is stuck in closed position.

When i reconnected the line to the WG i saw a peak boost of 1,2 bar before settling at 1 bar. Boost is coming on at 1700rpm, but does not go over 0.5 bar until 2200rpm.

I believe it's safe to assume that the problem does not have anything to do with the turbo.

Any thoughts?

Just some suggestions:

Your symptoms sound similar to that of a failing MAF sensor. Can you monitor it under load or try a known good sensor. On the P26 I think they're the same part number for both diesel and petrol engines. You could try cleaning it also but only use MAF cleaner and ensure it's bone dry before reinstalling.

Any black smoke on boost? Have you pressure tested the intercooler?

Out of curiosity does your model have vacuum controlled engine mounts?

Hi, and thank you for replying :)

I can try to log the MAF. I have looked at it earlier, but not knowing what I'm looking for it's hard to come to a conclusion :P

There is black smoke on boost if the car has been driven "nicely" for some time. But after a hard pull in 2nd gear it will not smoke until normal driving on low revs for a bit. I think that's completely normal for an old diesel?

Yes, the car has vacuum controlled mounts. Both of them are replaced, and there is no leaks. (Expensive mounts! :eek:)

I will try to get a log from the MAF in a couple of days. It is not failed completey, because it's even worse when i unplug it.

I'm following this thread with interest. I can't add much but I think your comments about black smoke are quite normal for this engine and in line with my own experience.

Martin
1998 V70 Tdi SE Auto 225,000 miles

Have a read of the following threads:

https://www.volvoforums.org.uk/showthread.php?t=209496

https://www.volvoforums.org.uk/showthread.php?t=217033

I know they are D5 related but just to give you an insight. There's another thread in this section, again D5 related, with regard to the control valve for the vacuum mounts having an adverse affect on performance when not functioning 100%.

Indeed , back when these cars were current and just afterwards it was quite common for this lack and power and in 9 out of 10 cases it was the Mass Air flow meter . and yes I had many more than 10 cases over the years ...

Intercooler about to fail or leaking when pressure applied to system maybe.

that would be noisy and blow oil mist everywhere :-)

I will take a look at the links :)

I will take a look at the MAF in VIDA. Updating you when i have some info.

There is a bit of oil residue on the exit of the IC, but I think that was a loose hose clamp. I have pressure tested the system and nothing alarming to find. Replaced a few hose clamps, because they broke when I tried to tighten them a little more. The leaks I found were very minor.