Having fuel system issues, I think..

lctmjw

New Member
May 28, 2006
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Overland Park, Kansas
I'm considering the purchase of another MKIII that a friend of mine is selling. The car runs okay, but it has some issues that haven't been easy for me to diagnose. Any help and insight is appreciated..

Mods on the car-
Walbro pump (unconfirmed), 550 cc injectors (confirmed.. well, at least they aren't stock), 1UZ AFM, Profec B, HKS BOV, Aeromotive fuel regulator, 3" exhaust turbo-back, FIPK ---No fuel management---

Problem-
Car starts and idles well enough, but it won't boost beyond 7 psi or so, and feels like it's hitting fuel cut. Check codes, and 21 (O2 sensor) & 34 (abnormal turbo pressure) came up.

No vacuum leaks anywhere.

I changed out the oxygen sensor with a known good one, same problems.

I don't believe that the AFPR is adjusted correctly, either, but I don't know what it's supposed to be set to. Fuel pressure was at 20 psi or so with vacuum line disconnected, 15 psi or so connected. From what I've read in other threads, this is low. I adjusted the FPR to 45 psi or so disconnected, 40 psi connected. The car ran considerably worse this way. Checked AFM adjustment screw, it's backed out all the way.

Any suggestions?