Fueling Issue - 2006 S80 2.5T AWD

[hypernon]

I have the most specific issue and I'm at a loss. About a week ago, I, in my infinite wisdom, did a muffler delete (cmon, it's a turbo 5, I had to). The drive after, the engine stumbled while coasting around a corner but recovered. About a mile later while coasting down a hill, it completely stalled. I pulled into a turn off, and scanned it with my code reader. I had a P0088 code, a fuel overpressure (I have since not had that code again). I had heard in the past that the PEM could have issues on P2s, and a previous owner had moved mine to the spare tire well. I thought that potentially the vibrations from the exhaust and maybe the dump pipe I added were causing issues, so I moved it up to the actual trunk and ran the AC with the seats down to help it cool down. I got home with that, thought that fixed it, and ordered a new PEM for good measure. The next day, still with the old PEM, I drove somewhere, parked, and went in. Came back out, started the car, idled for a bit, car stalled while parked. I tried starting back up, didn't work. I waited a while, started back up. I drove halfway home, stalled again while coasting. Waited a while, got the rest of the way. While I waited for the new PEM, I used ice packs to cool the PEM, and that seemed to help, with a single hiccup stall at a red light, started back up when the light turned green. Installed the new PEM the next day, went on a drive, no issues. Thought it was fixed. The next day, it stalled twice while maneuvering in a parking lot. When I get home, I figure that potentially the vibrations from cutting the exhaust stirred up debris in the fuel tank and clogged the filter, so I installed a new filter. No issues for 3 days. On day four (today) I start the car up for a quick drive, and get a sudden sustained stumble. I quickly step on the gas to raise the fuel pressure and maybe recover, which it does, but not without a ton of weird jerky spikes of acceleration. I pulled over after that, and it idled like nothing had happened. I drive home, no issues. Right now I disconnected the battery to maybe reset the ECU trims to see if that helps. The last two things I think could be causing it are the fuel pump or the pressure sensor. I'm thinking I should order a proper scanner with real time data (recommendations?) and a fuel pressure checker to see if the fuel pressure sensor is acting funny, but again, the only code I had was the P0088 high pressure, which only happened once. The common strain appears to be that issues happen during low load, maybe after heat soak.

[Vova585]

I am not a big fan of parts cannon, but when price is right, I am willing to go that route. I would order new Bosch pressure sensor($ 35-45??? ) and install it. With fuel pump it is difficult to diagnose without scope to see if wave form is equal on all commutator points of rotor. I am not an expert in s80 by any means so not sure if evil marketologs placed it in accessible location(below rear seat with nice access panel from up top) or they decided to make easy 1000 for dealer and said- "drop the tank to access". In case of later, look yootube videos how to cut an access panel in the body sheet metal to access from up top.
Since it is awd cars, have you noticed any relationship between how full your tank is and amount of stalling episodes? Awd tank is basically 2 tanks with fuel pump in one of them and transfer unit(or pump depending on the car) in the opposite end. Try to fill the tank and see if your problem will not be present. If while you are driving on 100-65% of tank you have no issues- you may need to inspect the transfer line.
Good luck

[Krons]

Another vote for the fuel pressure sensor, worth staying with Bosch as not terribly expensive.

[scot850]

Is the car an AWD? Surfbug1 had an S80 2.5T and it was FWD. He went through lots of fueling issues. He replaced the fuel pressure sensor on the fuel rail, bought a pressure valve to find his car does not have one on the rail, even though the parts drawings show one. He also swapped the PEM, but in his case the issue ended up being a the fuel pump where the valve is fitted on his car. Previous owner had fitted some Amazon special which was junk. Replaced with a Bosch unit and all good.

Neil.