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Author Topic: Showing lean, no knock good FP  (Read 4423 times)

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Offline bescurred

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Showing lean, no knock good FP
« on: October 26 2013, 03:59:50 PM »
That's what i've ran into...I've tried two different fp gauges.  One is a hood mount and I watched it during a pull and the other is rail mounted liquid filled.  Both set to 42PSI line off.  During a 3rd gear pull O2's (wideband and narrow) are showing in the mid to high 600's on only 13psi.  I took off the driver side manifold b/c it sounded like an exhaust leak and I couldn't find anything.  Slapped it back on and it still sounds like it but I'm not seeing it.  Manifolds are stock with no gaskets.

I have the wastegate backed off b/c I don't want to hurt the car.  Also air only blows out of at the feet and the dash.  I'm assuming there is a vac leak there.  Would other vac leaks combined with vent ones or exhaust manifold leaks cause the O2's to show low?

Mods are TE-44, 38lb bluetops, THDP dp, 2 1/2 exhaust, TT 5.7 chip left at default settings hotwired FP, AFPR. 
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Offline Steve Wood

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Re: Showing lean, no knock good FP
« Reply #1 on: October 26 2013, 05:43:13 PM »
So should we assume you are seeing 56 psi of fuel pressure at 13 psi of boost when the 02"s are in the 600's?

Leaking manifolds will cause the o2's to be lean but my experience is that it makes the largest difference below about 3000 rpm and diminishes above that
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Offline bescurred

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Re: Showing lean, no knock good FP
« Reply #2 on: October 26 2013, 05:47:25 PM »
Yup FP is good...It's a brand new ASHCROFT gauge from Gbody too...it does flutter some but thats from no liquid right?
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Offline Steve Wood

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Re: Showing lean, no knock good FP
« Reply #3 on: October 26 2013, 06:16:24 PM »
No, I doubt the flutter is from a lack of oil.  None of mine flutter.  It may depend if there is a restrictor in the gauge inlet or not.

I think I would start by finding the leaks.

Do a smoke test.  pour a little tranny fluid or brake fluid in a small container.  Crank it up and stick a penny or something between the throttle lever and the iac screw to get a fast idle.  Pull the hose off the fuel pressure regulator and dip the end into the oil...I always try to restrict the hose a bit so it cannot suck too much oil up and kill the engine...smoke should come out of any leaks.  Check both sides and the cross over joints as well as under the turbo
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Steve Wood

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Offline bescurred

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Re: Showing lean, no knock good FP
« Reply #4 on: October 26 2013, 06:18:55 PM »
Zip tie work to squeeze the hose a little to restrict it?
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Offline Steve Wood

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Re: Showing lean, no knock good FP
« Reply #5 on: October 26 2013, 06:24:06 PM »
should work or squeeze it with pliers
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Offline earlbrown

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Re: Showing lean, no knock good FP
« Reply #6 on: October 26 2013, 10:02:16 PM »
Quote from: bescurred on October 26 2013, 05:47:25 PM
...it does flutter some but thats from no liquid right?

Any change you have an Accufab fuel pressure regulator?
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Offline bescurred

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Re: Showing lean, no knock good FP
« Reply #7 on: October 27 2013, 10:31:49 AM »
Quote from: earlbrown on October 26 2013, 10:02:16 PM
Quote from: bescurred on October 26 2013, 05:47:25 PM
...it does flutter some but thats from no liquid right?

Any change you have an Accufab fuel pressure regulator?


No its an older one I think...looks like the ones that kirban sells


Accufab are the no bueno?
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Offline motorhead

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Re: Showing lean, no knock good FP
« Reply #8 on: October 29 2013, 06:32:27 AM »
What is your WB O2 AFR reading?
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Offline bescurred

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Re: Showing lean, no knock good FP
« Reply #9 on: November 01 2013, 01:38:34 PM »
Quote from: motorhead on October 29 2013, 06:32:27 AM
What is your WB O2 AFR reading?

Anywhere from 12.5 to 13.9
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Offline Steve Wood

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Re: Showing lean, no knock good FP
« Reply #10 on: November 01 2013, 01:50:47 PM »
welp, the wb is telling you the same thing as the factory o2.

Either the wot fp is not holding, or you would appear to have some cylinders that are misfiring to get it that lean
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Offline Steve Wood

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Re: Showing lean, no knock good FP
« Reply #11 on: November 01 2013, 07:14:27 PM »
what is the maf reading at wot?
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Steve Wood

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Offline bescurred

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Re: Showing lean, no knock good FP
« Reply #12 on: November 01 2013, 09:43:19 PM »
I will have to go back and look at it...I don't have the PL yet...it is next on the list but I do have the SM and WB....
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Offline Steve Wood

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Re: Showing lean, no knock good FP
« Reply #13 on: November 01 2013, 09:51:26 PM »
If it reads low, the ecm will cut the fuel down...and then you can end up with what you are seeing
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Steve Wood

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Offline bescurred

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Re: Showing lean, no knock good FP
« Reply #14 on: November 02 2013, 10:44:19 AM »
Okay, I'm about to get ol' girl out and see whats up...I kinda hope it is that.  I've been putting off grabbing a LS1 MAF anyways.  I know the horror stories about these stock style mafs  :x
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