I bought a 2005 xc90 t6 with a bad transmission. I pulled the engine and Trans to completely rebuild them. Transmission went nice and smooth with the Triple Edge Performance kit and with the engine I did pretty much everything down to the rings, bearings, all new sensors, cam solenoids, and I just bought a coil plug and wire kit to rewire the harness to the coil pack because the wire are looking very crusty. The problem I have with the engine is I have low oil pressure and the light will flicker after I drive for while at a stop and also the cam solenoid never activate at the higher rpms because of the low oil pressure causeing the CIL to pop up with the cam solenoid codes. I changed all the orings except for the oil cooler pipe in the pan simply because I didn't know too and didn't realize that they were there. I don't have any bubbles in the oil, I made sure to pump oil out of the filter before the first fire up to get oil pressure and there was pleant of pressure that shot out. The engine runs perfect with no noises except for this problem. It does on start up clatter for a split second I'm assuming because the lower oil pressure. Also I have had it a few times run flawlessly with full power and i can feel when it activates the cam solenoids. Sorry for the long write up I just want to make sure to provide all the info I can. I'm gonna try a thick oil this weekend as a suggestion from a guy I was talking to that owns a shop here I'm town but any help would be greatly appreciated. Thanks

 

Replace the oil filter and use the correct oil. If that doesn't help you may have an oil pump issue or a faulty pressure switch.

 

I got some Liqui Moly 5w40 and a volvo filter ordered and should be here this week, fingers crossed. The oil pump would be the only thing that I didn't replace, I thought about during the rebuild but read that they typically don't go bad. Thanks for the response. I will let you know what happens after the oil change.