2005 4.4i, Loses power \ stalls accelerating into tight corners?
 

Hey guys, I am killing time waiting on my wife so I have had no time to do any diagnostic work yet, hoping maybe you guys will give me some ideas that I can dig into once I have the X home and back in the garage.


Right after we left the house my wife said "oh shoot, I left my purse at home", so I whipped it around for a u-turn and as I went into the turn she lost power.. didn't stall, but fell flat on her face, I did a quick lift of the foot and as soon as she settled back down we were off to the races again???


Had this happen to me once before, very long time ago and never happened again so I wrote it off as one of those things... - now it's happened twice inside a few days and is very reproducable - but does not happen in a straight line. If I mat it from a dead dig she goes like madness, no hesitation what so ever, but add a corner, left or right hand, doesn't seem to matter and she's dead, flops over on her face, lift foot, settle down, peddle down and she goes again.


Where to start? Thanks!!

2005 4.4i, Loses power \ stalls accelerating into tight corners?
 

Sounds like fuel supply issue.

Fuel pump or FPR.

Check fuel pressure and see if it's dead flat stable. If it dips when you hitting throttle the o-ring in the FPR is shot or the pump is shot.

If the pressure won't stay overnight than the o-ring in the FPR is shot.

What is the fuel tank level?

Once the tank has less than 27L the fuel pump only sees 5L of fuel. And once you take a turn some of that fuel will slosh out of the fuel sump dropping the depth of the fuel considerably so the pump will hen less help on the suction side indicating more than likely it's the electric pump being weak.

If the problem goes away when half a tank of more it's almost for sure the electric pump

Interesting thought on the o ring and pressure, now that you mention that over the last half dozen starts or so I have noticed it takes just a wee bit longer to start than it usually does, hmmmm, 2 and 2 may be making 4 here on potential fuel pressure issue. Damn... will be tomorrow now before I'll now, was chasing a lean issue with my daughters car and cracked my fuel pressure gauge... Looks liek I'm getting new tools tomorrow :D

The FPR will hide a worn fuel pump for years. Basically the pump makes 60 psi, the engine takes 50 the leftover goes back to the tank to suction the left tank to the right.

When the pump wears out as long as it makes more than 50 it can ton the engine but will eventually fail to run the siphon jet.

When the FPR fails (usually due to EU regulations forcing BMW to use shitty o-rings), the symptoms are usual random hard starts also the pressure will waver from dead flat 50 psi.