fuel system puzzle: loss of power at highway speeds

[trimjimmy]

I have a 2005 xc90 T5 which I bought used off a car lot; no history available. It seems like the car was severely neglected over the last decade of its life; the engine oil, tranny oil, and air filter were filthy. Catalytic converter had frozen, and somebody had taken a grinder to it, I imagine to open some airspace. New cat, new filters, oil and fluids, cleaning the VVT solenoids, fixing some nuts and bolts issues, plus a good engine additive (Tribotex) all gave indication that the vehicle was sound, and wanting to continue its long and happy life.
I gambled on success (my 2008 xc90 V8 was still having its tranny replaced) and took it for a road trip from Southern Oregon to Idaho then through Montana and back to Roseburg; it drove like a dream, but with intermittent and rare episodes of air/fuel inequities: sometimes at highway speeds, when pushing into the gas pedal asking for more power/speed, the power would cut out. Not choking or gasping, and no threat of stalling, just momentary absences of response from the gas pedal. I quickly learned to make acceleration changes slowly, and downshift for climbing hills, which seemed to avoid or alleviate the problem. It was an incredible pleasure to drive: smooth, responsive, hugging the roads; the care wanted to LIVE.
However, on the the steep mountain passes coming out of Montana, after having driven for many hours at illegal speeds on winding Montana state highways (many rapid changes in acceleration, and many requests for power), the problem became worse. Pushing into the gas pedal brought no response, and the engine started stalling. Eventually I had to pull over, It was 10pm, I was unable to make the car go uphill at any speed, so I let it coast backward for half a mile to a way station which appeared to be my last chance to pull off before the pass. I expected to spend the night there, and get a tow in the morning. However, after some Marvel Mystery Oil and about 45 minutes of waiting, the car started up; I was able to drive around on a frontage road enough to get confidence that I could make the pass. There was a good mechanic in Post Falls ID I knew of, and if I could get the car up over the hill, I knew I could virtually coast to Post Falls.
I made it, got reemed for a late-night motel room, had the codes read at O'Reilly's in the morning, and listened to the guy behind the counter telling me that they all pointed to the fuel pump. As the symptoms were consistent with this possible cause, I didn't question it. I bought a new fuel pump (not OEM) and met my guy at his shop for him to replace the pump, which he did. I had to wait an extra day because the O'Reilly's guy sold me the wrong pump. I have no question with the mechanic's work; I trust him implicitly. Two days later, with a new fuel pump and back on the road, it seemed that the problem had been solved, except I had to drive with windows open to disperse the gas smell. I drove like grandma at first, but gradually regained my confidence. After about 3 hours, there appeared some slight gaps in asked-for power at high speeds, but again I learned to make changes slowly. However, driving through the Columbia Gorge, it became evident that the problem had NOT been solved. I had driven too far to go back to the Post Falls mechanic, and so limped forward to Portland. I picked the brain of the Meineke owner there, and had the fuel filter changed the next morning, Again, when I started out, everything was groovy, but after an hour I found the problem had returned. City driving was no problem. After an hour on the freeway, if I pushed for acceleration I would get a little, but then suddenly NO power, and no response from the gas pedal if I kept pushing. Only by backing off and lightly feathering my acceleration was I able to get back to Roseburg.
I have since replaced the fuel rail pressure regulator, and both VVT solenoids, and had the fuel system pressure checked. In 6 months the gas smell has not gone away, and presents itself most strongly under the car behind the driver's door. I smell gas inside the cab, too, again most strongly behind the driver's seat, but it is faint and mostly tolerable. Nary a drop of gas on the driveway by the way. My amateur attempts at code reading bring up P0017: camshaft alignment. Basically, the VVT solenoids.
I'm wondering if anyone had any experience with similar symptoms...
JIm J

[ggleavitt]

Wow, you replaced a lot of parts.

Gas smell. Someone has not cleaned the tank channel well before re-assembly and/or the o-ring and cover ring were not put together and properly tightened. You'll want to get that resolved. There are two cover rings on the tank and depending on the amount of work that was done the level sensor would have also had to come off to ensure that the ejector lines from the pump to the other side of the tank were routed correctly and not kinked).

Pump output is controlled by a module (PEM), part of a demand system that manages pump speed as a function of a number of inputs (FPS sensor feedback as one). Looks like you replaced pretty much everything except the PEM. Was this ever checked as part of the troubleshooting process? Module should be under the seats in the area of the tank, looks like this (gratuitous photo from the internet):

I might have another look in the area of the tank and consider replacing the PEM with another while the tank rings get opened, tank channel fully cleaned, and o-rings reseated and properly tightened. Might also be something completely unrelated but if I still had this issue after all of the other parts you're replaced, I would be looking at the electronic module which controls the pump output and that's the PEM.

Speaking of which, something in the back of my head suggests that the fuel pump will still produce a partial output if the PEM is not working, this might be served via the internal ejector pump. Forum member jimmy57 can probably provide some insight into this and it "could" explain the sputtering and cutout at full pressure.

[abscate]

It’s very easy to kink the fuel lines on these cars and induce high demand fuel starvation. User shockwave wrote up a great post on this a few years ago