You likely have a mechanical fuel delivery issue. That's the good news.
WAY too low idle fuel pressure. should be around 60-65 if I recall. (with vacuum line disconnected)
any way to monitor fuel pressure at WOT ?
things to check:
swap FPR (not cuz its likely to have failed, but because its easy, also, check the screen on the bottom of it for possible debris)
kinked fuel lines running back to tank. (sometimes they can get crushed somewhere along the bottom of car)
Pull fuel pump. Check the return lines (the long ones that loop around) for kinks. repair if needed
Check the fuel pump line from pump to lid, people like to use the wrong type of line, or dont install correctly, and it will kink, or split open at a stress point.
Change fuel filter, (in my experience this NEVER helps unless its literally never been changed in 15 years, but its cheap and easy)
Lastly, inspect the fuel pump itself.. A lot of these are being sold with a shitty pressure bypass mod that falls apart and basically just puts a big old hole in the top of the pump..... I personally think modifying a fuel pump like this is about the dumbest thing... Walboros are already sketchy in my book, no need to introduce further amounts of sketch.
If all this checks out, replace the pump anyways, or, you can stick one inline in the engine bay and test with that... Thats how i determined I had a failed pump after checking/fixing everything else. (see wall of text below)
I had a similar problems on both of my big turbo carsr. WOT had very lean AFR leading up to peak torque, then it would pull timing like mad, and start dumping fuel.
One car, same as yours, low pressure at idle, you could drive around ok, but push it, and bad things happened.. I had no AFR guage, and no real tools to diagnose... I did however install a walboro fuel pump "kit" that included a shitty piece of hose (tyrolsport kit i think) and it turned out it was far too short, and split open at the fitting.
My S4 had similar issues.. get into peak torque and it would pull timing etc.... again, no AFR guage (yet)... but I did have a nice fuel pressure guage... pressure was actually ok at idle... but if I got on it, the pressure actually started dropping as i got into boost.. a LOT.
Traced the problem to both return lines being kinked shut in the tank.. And a subsequently burned out pump, or, the pump was defective from the get-go... And this was just a regular walboro 255.....
I went 044 after that.. Ill never run another one of those cheap pumps again.
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Originally Posted by jimmer009
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