Driving home last night on a major Interstate at the posted 65 MPG, my XC90 w/ 240K miles suddenly lost power (though not entirely) and began vibrating. The Check Engine light illuminated, began flashing, and after about 30 seconds, went off, though neither the performance nor vibration stopped.

The car struggled on inclines, improved on decent, and I found that using the manual shifting mode, I could downshift, raise the RPMs to around the 3,000 RPM rate and gain some torque while maintaining posted speed.

The Check Engine light re-illuminated several times, but also extinguished itself shortly thereafter, often blinking, not steadily lit.

Given the hour of the night I elected to limp home on what seemed like 4 out of 5 cylinders.

I've never experienced a sudden change in performance while driving at speed with this car, and have no idea the cause.

Hoping you have some advice. Thanks.