it all started slowly, motor issues, 2,4T, MY2001

Series2a · Post by **Series2a** » 13 Jun 2019, 19:06

Hi all,
I am new to this forum, but read me through a lot of interesting posts.....

My Volvo is a XC70, 2,4T, 02/2000, MY 2001, (the 528th V70II build

), with 400.000 km and no issues until about a year ago.

It started with a light surge, sometimes, not very often, perhaps every 20th times of driving. It appeared a bit more often after a couple of months and I knew it would surge when I started the motor, because it would change idle (rev up to 1.200) after a couple of minutes, just for half a second, and then come back to the normal very smooth idle at 700... If it did not do this, it would not surge later, while driving.

About 10.000 km ago, it started to do this nearly every time I drove.
There are no motor related codes on VIDA.
I changed the MAF sensor, and still had the same issue.

I realized that there is a severe loss of power and more surge when the engine is hot, about 96 degree (celsius) cooling temp.

About 5000 km ago, the loss of power when hot became a constant issue.

Actual behavior:
Now, when the motor is still cold, it has full power, with a bit of surge, and when above about 90 degrees, it feels a bit as if there is no turbo charging. (I hear the turbo whining, as I hear it since about 100.000 km, but there is only about 50% of the normal power...) The change of this behavior is still announced by a rev up during idle for half a second...

I changed the TCV three days ago. It acts a bit different, but still nearly has the same behavior, normal power when cold, loss of about 50% power when warm.

I manually moved the wastegate actuator link, it seems not to be stuck.

My next step would be to have a look at the CBV, if the spring is perhaps tired or if there is a hole in the diaphragm.
I also did not check the pressure hoses after the turbo.
I could buy a cheap turbo gauge and fiddle its supply hose into one of the pressure hoses, to see turbo pressure while driving.

The ECM still does not throw any codes on my VIDA..... (I am not a VIDA expert, many of the values shown do not tell me much...)

I would change some more sensors if I would be in Germany, (I am German), but currently I am living and working in Casablanca, and took the Volvo with me....(The TCV cost about 200 Dollars here in Morocco)

Sorry for this far too long post, but now you know the important parts of the whole story.

I am driving the car every day, it is not really an issue in normal traffic, its just annoying not to know what is wrong, and kind of fun searching and trying .....

What would you do?

Cheers, Michael

Post by **precopster** » 14 Jun 2019, 06:32

I had a similar issue with my Feb 2000 build T5 (P2 model) due to the throttle.

When using Vida you can take a look at throttle position 1 and 2 separately in ECM or ETM Parameters. Check that you can see both throttle angles changing in a linear fashion when depressing the accelerator. This is easier said than done because you have about a 10 second window from when you place ignition in PosII.

Also try to perform an ETM test in ETM Advanced. Anything more than 2-3 degrees of difference is not good for a non-contactless ETM.

Also what is the MAF flow rate at idle ? Should be between 12.5 and 14 KG/HR.

Check the MAF flow rate at cold then when hot. Also check charge air temperature. The sensor is on the pipe leading to the throttle. It's the tall sensor with a cage closest to the throttle.

Series2a · Post by **Series2a** » 14 Jun 2019, 12:53

Thanks a lot precopster!

I just performed the test with the 2 throttle position sensors, the difference value is 0.32 degree average, and 0.58 degree maximum. So that should be ok.

Also measured the intake air flow when more or less cold, and when cooling temp at 104,0 Celsius, its both more or less the same, says

10.5 to 10.7 kg/hour. (what does that mean in comparison to the values you gave me?)

Also measured the intake air temp, it says 46,5 degrees while outside temp is at about 18 deg (basement garage) and coolant temp at 104 deg (all celsius) The sensor itself looks a bit oily, but not dirty or broken.

Still no ECM codes...

I could somewhere upload the videos of the display, but I think you get along with the above?

Cheers, Michael

Series2a · Post by **Series2a** » 26 Jun 2019, 16:59

Hi again,

as there are still no EMC codes, I inspected the turbo and decided to take off the CBV. It was quite a difficult procedure with nearly everything still in place but after a while the work was done and I discovered a small hole in the membrane. I replaced the original CBV with a self made blanking plate. I thought this was the problem, but:

The behavior of the engine didn't change though, still it has full power when cold and about half power when warm.

Then I took of the Evap tubes and the TCV and closed all tubes, to minimize possible leaks...

Still, the engine develops only about half the power when warm.

Does anybody has an idea what may cause this behavior, it does not seem to be related to the air intake.

Could the EMC lower the fuel rate when the engine is warm? (though it does not feel like this, its not surging, its just not accelerating with the same power when warm.)

Cheers, MIchael