01 Pathfinder looses power

[Swanicyouth]

Today I was driving along the freeway. I went to pass someone and all of a sudden my 01 PF 4x4 lost power. By lost power, I mean would not accelerate past 30 miles an hour and gets there very slowly. This is not a situation where I "need a tune up" or "better gas". Something happened all of a sudden. There is also a wining noise that started with this, but it only happens under load - so I can't pinpoint it in park. There was no CEL light and the engine idles smooth, the problem is only under load - I had a hard time getting it home up hills, as it accelerates very slowly. But, its fine up to about 10mph - when it starts to loose power, it starts to make a "whiny" type noise, which seems to be coming from underneath or the right side of the engine. I can't pin point the noise, because it's only doing it under load.

Revving the engine in park, it seems fine. There *seems* to be good pressure at the tailpipe. I shooked the exhaust and nothing internal seemed loose or broken. But, there is that "whiny" noise from under the vehicle, hardly noticeable when revving in park, but noticeable at RPMs over 2000 when driving.

Im thinking it could be one of 3 things:

1. Power Valves

2. Exhaust / cats plugged

3. Torque converter failure

My question is, if it was power valves, wouldn't the engine make noise when revving in park and not idle right. That doesn't seem to be the case. The fuel filter was changed about 6 months ago, and this did happen suddenly, so I doubt it's that. Plugs were also changed around that time.

Any comments, advice, help is welcome. Thanks!

[Towncivilian]

Check for intake air leaks by spraying brake cleaner around the intake with the engine idling and listening for a rise in engine RPM.

Perhaps try cleaning the MAF sensor and throttle body as well.

Power valve screw ingestion is a possibility, I would try to check those as soon as is convenient for you. Also check the condition of the transmission fluid. It should be red and not smell burnt.

[buhaw12]

Sounds like a transmission issue to me. I wouldn't think torque converter though if it's fine up to 10 mph.