Engine: B5204: Losing power around 2.5 - 4k rpm S80 2.0T

[flakeypaul]

Hi,

Here goes my first post on here - it would be for a problem wouldn't it!

My (newish to me) Volvo S80 2.0T SE Auto @ 137k has a strange issue with the power delivery.

Basically at higher speeds (50mph +) when accelerating, the box kicks down smoothly but then the engine hesitates hugely between 2.5 - 4k rpm. Whilst revving through this range the acceleration 'surges' for about a second, then the power dies, then it surges again for about a second. Once it gets beyond 4k rpm it pulls strongly and smoothly to the red line. This seems to get worse the further I drive the car.

From what I can tell the turbo is not in bad health - there's no screeching noises or smoke, and it does rev cleanly in lower gears. It does this whether accelerating using my foot or using the cruise control. I'm going to give it a service this month, it had a major service 10k ago, but I like to know what's in my engine!

Has anyone experienced this or have any ideas? I'm guessing either the waste gate sticking open or an actuator leak somewhere?

Thanks
Paul

[flakeypaul]

Well no replies but I got there in the end!

The boost solenoid was clogged solid. I remove the three hoses (completely), cleaned the solenoid out with carb cleaner (amazing how much crap was in there), and flushed the hoses out with carb cleaner too (ran through for about 30 seconds before the fluid ran clear.

Suddenly I have a car that wants to accelerate! When I said above it pulls strongly to the red line above 4k rpm I was wrong - it wasn't pulling cleanly at all (it just felt like it coming from a 1.6 C-Max), but it does now!

[Jonny5isalive]

Hi Paul, pleased you got it sorted in the end. I hate it when things go wrong. Happy (quick) motoring.

[flakeypaul]

The plot thickens!

Well when the engine is not fully warmed up (i.e. driven for less than 30 minutes) all is well. However once it warms up the 'surging' returns, albeit much faster.

Whereas before it was surging perhaps for a couple of seconds, then loosing boost, then surging again, then loosing boost, now it surges every half a second or so.

It's as if its generating too much boost and then opening the waste gate to bleed it off, then doing it again and by unclogging the solenoid it's just made the process much faster.

Anyone had any experience of this? My first thoughts are a dodgy boost solenoid or badly adjusted waste gate.

[Shires]

What state is the vacuum piping in? If the boost solenoid was clogged with muck it had to get there through the pipes first. The fact that it happens when your car is warmed up is interesting, might the heat be softening the piping?

I had similar problems to yours on a V70 2.0T with 100,000 miles - surging when applying throttle. All the vac piping on that car was perishing and easy to deform with the fingers. I replaced it with fuel hose and cable ties in place of hose clips, needed two sizes, 5mm and 8mm perhaps but the memory is fuzzy on that.

Other things I did while trying to sort it included taking off the intake manifold and cleaning out all the little ports (clogged), flushing out the oil trap and ports on the block (totally clogged), and cleaning the throttle (filthy). I also cleaned the boost solenoid too as you did. Not sure which of those cured it for me - maybe a little of each. May well not be the problem on your car but some food for thought anyway.

[flakeypaul]

I've just checked the vacuum pipes after a run - they're not cracked or split but much easier to deform when the car is hot than they were when I cleaned them (when they were cold) so maybe they're original and just need swapping out.

Next job for me to do is the PCV system as it's blowing a little out of the dipstick, so I'll give the whole manifold and throttle body a good clean up while it's all off the car and see what difference that makes (car is on 139k). Might even sump dump the ATF while I'm in there as there's no record of it ever being replaced (plus it's brown not red).

Thanks for the help - I'll update in here once I'm done (assuming I don't screw it up!).

[DT19]

I've just bought a set of silicone pipes to replace my old vacuum pipes this weekend. I might have a look at the boost solenoid as well. Where abouts is it?

Also Paul, is you surname Flake by any chance?

[flakeypaul]

On my S80 it's attached to the air filter housing (1 x electric plug and 3 x colour coded vacuum pipes attached).

It just clips and on and off, there's no screws to remove. Two of the pipes (to the waste gate and to the turbo) are held on with clips, the blue pipe to the air intake pipe by the turbo is not clipped on on my car (although I'm going to get new clips for this just in case).

No my surname's not Flake - flakeypaul's just a very old nickname :-)

[owyn]

Out of left field a bit, is it a misfire? Bad spark plugs maybe?

[flakeypaul]

It doesn't feel like a misfire because when when it's cruising it's very smooth, it's only really at half - full throttle (when hot) that it does it. Plus it's doing more to the gallon than it's supposed to (22mpg round town and 35mpg on the motorway).

That said though the plugs and air filter are 16,000 miles old looking at the service history (I've had the car for 5 months and done 6,000 miles in it) and there's no documented fuel filter change, so these will all be done when I replace the PCV system as I plan to drop the oil in case anything bits break loose and drop in when I clean the ports so might as well call it a full service.

I'll change the vacuum pipes first and see if that does it. Whatever sorts it I'll report back here for reference. I'm determined not to take it to a dealer!