hello my volvo v40 b4204t3 ...have problem ... somtime my engine runing lean ... maybe after 15 min working normali .. than agan lean short trim +10 +17 ... when disconet evap valve ..short trim show normaly but engine show error p0444 ... vaccum leak not find ... wher it problem!?

 

I had the same issue, replaced your fuel filter and clean/rebuild your fuel presure regulator and you should be good

 

vacuum leaks can be hard to find - you may need to do a smoke test. could be lots of things - vacuum hoses, cracks in a t connector, crack in an air boot, injector seals and even all the way back by the evap cannister (in front of the right rear wheel). The P0444 points to the evap purge valve - easy to replace, if I recall its on the left side (drivers) of the radiator. Not sure about rebuilding the fuel pressure regulator - there's a diaphram which can tear but that usually leaks fuel into the vacuum line or allows the fuel rail to bleed off pressure making for difficult cold starts. can't hurt to try and clean it (it plugs into the side of the fuel rail).