Engine Hesitation
 

I have a 2005 Volvo S40 T5 AWD. While on the highway the car has started just cutting out. I watch RPM and they dont drop like engine is dying its almost feeling like the fuel is getting cut off then it jumps back on. Sometimes you can feel it when its about to happen like a miss but I have changed the plugs and old plugs looked great so its firing just fine. Now I admit this is my first turbo car but I am willing to learn. I have read hours of stuff on the forums and asked fellow mechanics. The kicker I had a P0101 code which is MAF sensor performance out of range I believe. I had code cleared got MAF cleaner from CRC cleaned sensor and checked all vacuum lines. I had a smoke test done to see if I had vacuum leak and nothing. From what Ive been told that the TCV on this car seems to go out especially in hotter climates as I am stationed in San Antonio. When I spoke to a mechanic at Volvo when regarding the part if they had it on hand he advised me he dont feel this will fix the problem. Now as this problem has been getting little worse and more prevalent I have noticed my boost gauge barely gets any boost at all. If I get on it then at best I get maybe 4 and hope it dont hesistate on me while doing so. I was pretty certain it was a TCV until the mechanic at dealer told me he dont believe it will work which led me to research more. Some common problems are fuel rail pressure sensor as the symptoms seem similar but no code and not sure how this could affect my boost. I just want to make sure I fix this correctly and I did the research as best as I could, but this is my first Volvo. I have a BMW as well to drive till gets better but I love driving this car and figured someone here would have an idea or direction to point me in. I appreciate any help guys. Take care.

Replace the MAF.

You cleared the code and it has not returned?

I have cleared the code and it has not returned. I had the MAF replaced already. I ordered a fuel rail pressure sensor the volvo mechanic mentioned my symptoms are on par with one on its way out. He advised me the TCV wouldnt cut out like the or make the engine cut out. My question is how does the fuel rail pressure sensor affect my boost if any? Since i have been having problems with this engine hesitation i have been watching my boost gauge and i rarely ever get any boost unless i get on it which 4 is what i get when i use to get about 9-10. I appreciate your feedback so far guys. Its a learning experience for me.

You know how the old S40's had a fuel pressure regulator? This is old school stuff. Standard issue FPR at the end of the fuel rail to regulate pressure. The new S40's are way different. Now instead of a FPR there is a fuel pressure sensor whose feedback controls the voltage sent to the fuel pump to regulate pressure! Are you kidding me? Seems an extremely complicated method. It does work though. As long as that fuel pressure sensor is working properly. Let us know if the new sensor cures the problem?

well i got the fuel rail sensor but the gasket didnt seal all around it so it kept leaking fuel...then i tried to back the bolt out and tighten it only to have the stupid star nut strip..so i gotta tap it...i hate star bolts so bad..i will keep everyone updated so far..i appreciate any and all feedback so far

Update the fuel rail sensor did the trick. It actually is running better than when I first got it. I would do a fuel pressure test on your system as you might not be getting the most out of your car. I found a vacuum leak as well fixed that and now she is running great.