Cut in/out under load

[IronMike]

2007 XC70 AWD 126k. All Volvo maint done, including timing belt and PCV system.

Generally runs great/strong. However, suddenly there's an issue where under acceleration there is a severe cutting in/out of the engine. I was hesitant to describe it as a misfire, which would be more subtle I would think. This behaves almost as if there's a misfire of more then one cylinder at once, or the fuel pump is kicking on/off. Revs and pulls very strong, otherwise and cruising on highway is smooth (though the issue may just be less noticeable), idle is smooth, starts fine.

If it's the fuel pump relay, it would happen all the time I imagine, like it did on my 740, not just while under load. Thoughts?

If it's the fuel pump, that might make more sense, but do they fail intermittently during operation? In other words, if it's a fuel issue, why does it still pull so strong.

Just looking for places to start. I don't mind swapping parts that go bad typically at this age/mileage on this model, we like the car and know we'll have to put some coin into it, but I prefer to do it myself.

Thanks!

Mike

[IronMike]

More info: Happens more under heavy load but low rpm. So, going up a steep incline with no downshift. If I go to manual shift mode and downshift, takes off like a bat out of hell. Still some of the "misfire" but no where near as worse as the low rev higher boost scenario (at least I assume it's higher boost).

[537playing]

It may be the fuel pressure sensor. It showed up on my VIDA and I replaced it. No more spotty hesitation symptoms.

[IronMike]

Thank you!

[Edwards]

Would check the spark plugs first. Check the air filter isn't clogged from that strange exhaust thermostat under the airbox. Pull codes and if you get 113 and 115, which is what is sounds like, then take the intake manifold off and clean all the negative electrical grounds.