Engine power loss only on freeway drives

[Connor31]

Hi guys, hopefully someone can help me out as this problem is driving me insane.
My 2012 Vito 110CDI drives great around town, pulls away nicely, no weird noises, never fails to start and fuel efficient.
However, on longer trips (which is why I bought the damn thing), it’s randomly loses power after sitting on about 110km/h. This can happen after 1 hour of driving or after 4. The revs stay up but I lose speed quite dramatically. When I pull over and let it rest for 15 minutes it seems to drive okay again until it gets stressed and it can happen again.
First garage could not source the problem as no error codes were showing.
Second garage, I had the DPF sensor replaced and system regened but obviously no luck. It seems to be heat/stress related...

If anyone has had similar issues and can enlighten me of solutions or anything that may help it would be greatly appreciated!

Sincerely, a frustrated Vito owner

 

[V6Matty]

I’ve something similar with our little W169 and it’s always down to the loss of boost, have a check you don’t have a leak somewhere

 

[Connor31]

Thanks for the reply, Matty. Will do. Only thing that has me stumped though, is that it drives and accelerates perfectly until it’s on the freeway for a while. Wouldn’t a leak show symptoms much earlier when trying to accelerate?

 

[oigle]

"The revs stay up but I lose speed quite dramatically." How is that possible?

 

[Connor31]

"The revs stay up but I lose speed quite dramatically." How is that possible?

Hi Oigle, if I shift down gears the revs still climb higher but my speed drops. They obviously drop a little but still remain relatively sound but with no power

 

[oigle]

Makes more sense mate. I'd be inclined to check out the MAF. They can do odd things at times.

 

[Connor31]

Cheers Oigle, I’ll add it to the list.

 

[Connor31]

Also, could it possibly be a fault in the coolant system? As it only seems to happen when under more stress and higher soeeds

 

[V6Matty]

Other thing to look at will be sticking actuator or the turbo, that would maybe explain while it’s fine to start and then after getting warm (everything expands) it stops moving freely and the ECU shuts down the turbo

 

[Connor31]

Thanks for the prompt reply once again Matty. It’s booked in next week so I’ll keep you guys updated.