Hi all ... have been experiencing a strange acceleration issue with my wife's XC90....

...about a month ago brought it into Volvo because it would sometimes seem to get "stuck" in a high gear from a stop or rolling start, accelerating extremely slowly (imagine driving in Winter mode). Even with the accelerator floored, it wouldn't kick down for a good 2 or 3 seconds. I figured it was either an ECU programming issue, the fuel pump, or transmission. They were initially baffled, but finally found a few cases nationally that listed the OIL pump as the culprit ... apparently rattling, triggering the knock sensors in the engine and cutting fuel. They replaced the oil pump and all seemed ok for a few weeks.

Over the weekend the issue reappeared, and now it's starting to happen more frequently.

Has anyone experienced something similar? If so, any clue as to the ultimate fix?

Could it be the fuel itself? Volvo lists 87 as the minimum octane, though 91 is recommended. I can't believe using the acceptable posted octane rating would cause knocking.

Thanks in advance for thoughts or insight.

Cheers,
Roc