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Sudden lean condition, need help.

Old 05-26-2005, 09:03 AM
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Default Sudden lean condition, need help.

OK, so I have been running the hack with 450's for about 9 months and it has been running great. I dialed the VAFC in on the dyno with a wide-band so my settings are good. All of a sudden, yesterday under a full boost run (~11 psi) the car starts to feel hesitant under full acceleration, like it possibly is detonating, and my A/F gauge stays in the lean section all of the time. Normally the gauge hovers in the stoich section and is rich under full throttle, rarely ever lean. Any suggestions? I have no CEL and the car seems to run fine out of boost or under lower boost. Is there a possiblity that my resistor box could go bad? Should I just go back on the dyno and retune the VAFC? I checked it and all of the settings look the same. Any help is greatly appreciated. I have a spare P28 that I need to get chipped for Uberdata, maybe this will fix my situation. I'm just confused as to why it would start doing this all of a sudden. Should I get a compression test? Would that have any thing to do with it? Please help.
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Old 05-26-2005, 09:22 AM
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Default Re: Sudden lean condition, need help.

if u can get a hold of a wideband that would probably be best
a compression test wouldnt hurt unless u ---- something else up when ur doing it
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Old 05-26-2005, 11:05 AM
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Default Re: Sudden lean condition, need help.

Maybe your fuel pump is starting to go? Only at WOT you say?
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Old 05-26-2005, 11:09 AM
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Default Re: Sudden lean condition, need help.

Its a new walbro that I put in at the same time as the injectors and the hack. I don't think it could be the pump. Yeah, at WOT I get some hesitation in the upper RPM range, and at any throttle position, the AF meter stays lean.
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Old 05-26-2005, 01:58 PM
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Default Re: Sudden lean condition, need help.

did someone touch your vafc settings?
check for fuel pressure, fuel leaks, check your fpr, check timing. maybe one of the injectors is on it's way out?
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Old 05-26-2005, 04:02 PM
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Default Re: Sudden lean condition, need help.

Running a B&M FPR?
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Old 05-26-2005, 05:28 PM
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Default Re: Sudden lean condition, need help.

Yes, I am running a B&M. I never thought of that.
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Old 05-26-2005, 08:55 PM
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Default Re: Sudden lean condition, need help.

it's hung open, check your fuel pressure.........another clue is the smell of gas INSIDE the car, becauase so much gas is being bypassed back to the fuel tank.

I now run a Aeromotive instead of the B&M POS.
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Old 05-27-2005, 12:06 AM
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Default Re: Sudden lean condition, need help.

Mista Bone may be on to something, but from my experience the only time my a/f would read lean no matter what is when one of my plug wires popped off.
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Old 05-30-2005, 02:55 PM
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Default Re: Sudden lean condition, need help.

Checked plug wires and fuel pressure is OK, according to my underhood gauge, although i haven't checked pressure under WOT. Is it OK to peg the throttle while under the hood looking at the gauge? Or does the car need to be under a load? I'm still stumped.
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