S80 T6 lacks power

[Loddzz]

Hi there

I’ve had my s80 T6, 2003 for a bit over a year now, and i’ve had several problems with it...

But this problem i’ll need some help with.

Car revs up to 1500 for a few seconds after start, then drops down to normal.
When driving on higher revs, kick-down, it doesn’t give full power and starts to hesitate and lag(?) until it gears down to normal revs again.

I’ve changed spark plugs, ignition coils, air filter, and vacuum hoses to the TCV.
Also, there’s only one code, P0420, but i don’t think it’s connected to my rev issue

[SuperHerman]

The code is saying you have a Cat issue - could be O2 sensors, bad cat or a vacuum/air leak.

Did you check the small hose that branches off the T coming from the TCV. So one line goes from TCV to the T, one short one (3-4 inches goes to Bank 2 turbo) and the other goes to a metal hard line that runs to Bank 1 turbo (also a small hose down there, but this one does not fail as often). Look at the 3-4 inch line as they go bad. Mine crumbled and was causing similar issues.

[Loddzz]

Yeah i know what the code means, but the cat still work properly, they check the values at the annual inspection.

I’ve already changed all the vacuum hoses to and from the TCV. The old ones was hard as rock and crumbled when you just looked at them...

I’m thinking Turbo Pressure Sensor maybe, but i can’t locate it...

[SuperHerman]

I went through the same problems with my 2004 XC90 with the T6 (same engine)

I doubt it is the Turbo Pressure Sensor. I would think it would throw its own code, but I am not sure. It is located on the lower intercooler plastic pipe inlet area. Standing, looking at engine bay, look down on radiator on your right side (car's actual left side) and look at the edge of the radiator then follow it down. Below, if I recall correctly, the transmission cooler line, you will see the plastic tubing going into the intercooler on this side. You will see the Turbo Pressure Sensor there - it is secured by one bolt and will have a wire harness going to it. It should be a square shaped sensor. It is a very easy part swap.

Two possibilities. First the O2 sensors or cats are in fact bad. You say they are working correctly so moving to the second possibility. I think you have an air leak issue as that could cause the code you are having and if the air leak is in the turbo pressure line it will knock them out (explains the lack of power). Best approach if you had a scanner with live data would be to read the O2 sensor readings to see how they behave and also the fuel trims. The fuel trims will tell you if you have unmetered air entering into the system. From there you could focus on bank 1 or bank 2 from the information.

On my XC90 I changed out everything (including the turbos) and could not find the problem. In the end the problem was the shop that did some work on my car earlier screwed up the hoses on the Turbo Control Solenoid, flipping two hoses. Once this was rectified the problem was solved. My code was turbo over boost - no O2 sensor or Cat codes.

There are some hoses under the intake manifold which would be worth looking at - also some check valves and a sensor. Did you check to make sure all your plastic plumbing running over the engine is properly secured at the clamps and have no cracks at the seam? They do crack at the seam over the years and let in air. Without any special tools the best approach is to check all your plumbing - plastic and rubber. Go over each one carefully - remove, inspect and reinstall to make sure done correctly.

[RickHaleParker]

P0420 Possible sources

• 1. Misfiring
  2. Air leakage in the intake system
  3. Air leakage in the exhaust system
  4. Faulty fuel pressure
  5. Uneven compression
  6. Anything that messes with the air fuel ratio.
  7. Anything that messes with the burn efficiency

[Loddzz]

I´ve found this "guide" for locating the Turbo Pressure Sensor, here on the forum, but i
don´t have any connections on that pipe, as in the picture below.
Where else could the sensor be located?




And i don´t know if the O2 Sensor is bad... I only know that the cats are working since the values are still good.
All the plastic tubes over the engine are good and tight. I´ve removed them several times for painting, changing
spark plugs/coils and so on.

This is what the live data says,
Bank 1, Sensor 2
Bank 2, Sensor 2

[Loddzz]

Okay, so today i put an adapter on the O2 Sensor that was giving me the P0420 code, just to
get that annoying CEL to go away.
This is the results

Before:


After:



I also took a look at the Fuel Trim, Short term/Long term, B1/B2
But it doesn´t say very much to me


Looked for any air leaks all around the engine, but i couldn´t find any... And while i was under
the hood, i took a photo of the tube where the Turbo Pressure Sensor should
be. I don´t have any there, as you can see



So, the P0420 code is gone(i hope), but it still hesitate on the Kick-Down...

[SuperHerman]

On the last picture you posted - follow the plastic piping to the radiator (see my prior post) and you should find the turbo pressure sensor.

[Loddzz]

Okay, i found it now
Is there any way to test it tho?

[SuperHerman]

I don't think it is your problem. Not sure how to test it, but you can try unplugging the harness and seeing if you develop a code. That will at least tell you the computer knows about it and it is working in some capacity - assuming it throws a code.

You need to do some reading up on fuel trims - optimal is around 0%. I think you have unmetered air entering into the system. See here: https://www.obd-codes.com/faq/fuel-trims.php.