Tuning running lean - Ford Mustang Forums : Corral.net Mustang Forum
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post #1 of 9 Old 03-12-2019, 05:50 PM Thread Starter
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Tuning running lean FIXED!!!

I am having a problem tuning my car. When I datalog it my STFT are perfect on passenger side na nk 1 and on bank 2 it is differentiated lean by 10pts. I checked for exhaust leaks and smoked for vacuum leaks seams like 100 times. Has me thinking that maybe the way I have my fuel lines plumbed that the fuel rail pressure sensor is not getting a correct reading because it is before the the bank 2 driver side rail is being fed. I had injectors flow matched and also swapped them side to side with no change. I also swapped o2 sensors side to side with no change. Sometimes When I do a idle log the tune is spot on from bank to bank then if I shut the car off and start a new log 10min later the tune is off again.. WTF. I have Edelbrock fuel tails with Vic Jr intake

So fuel is fed from
factory line with regulator in to
8an on the p/s rear fuel rail out to
p/s front rail
crossover to
Fuel rail pressure sensor on d/s front rail
Then it feeds rest of d/s rail


1999 Mustang GT Convertible
4.75 MMR 750se 10.5:1 CR Notched Pistons
Ported PI Heads CMS Turbo 2Cams Eddy Intake 75mm 60lb inj Twin Cobra Pumps Modified FPDM
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post #2 of 9 Old 03-12-2019, 06:50 PM
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If the fuel rails aren't tied together front and rear it's possible that a cylinder or two could be running lean.
I have my fuel system plumbed like the top view where both rails are tied together at the front and back.



Lean bank doesn't necessarily mean less gas is getting into those cylinders it could mean:
1. That bank is getting "more" air than the opposite bank...
2. The opposite bank is getting "less" air than the "lean" bank.
3. etc..


ks

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post #3 of 9 Old 03-12-2019, 07:16 PM Thread Starter
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Should of mentioned I am running returnless.


This is how I think it needs to be

https://pin.it/no5gf3xl7oso3w

1999 Mustang GT Convertible
4.75 MMR 750se 10.5:1 CR Notched Pistons
Ported PI Heads CMS Turbo 2Cams Eddy Intake 75mm 60lb inj Twin Cobra Pumps Modified FPDM
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post #4 of 9 Old 03-13-2019, 12:27 PM
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you already have the same thread started in tuning section?

89 GT gr-40, KB2200(10psi), tweecer R/T,LC-1, 22gal cell, w/tailpipes.
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post #5 of 9 Old 03-13-2019, 01:00 PM Thread Starter
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Quote:
Originally Posted by indy2000 View Post
you already have the same thread started in tuning section?
Yes was looking for help more so with the fuel line setup in this forum thatís why I posted here also.

1999 Mustang GT Convertible
4.75 MMR 750se 10.5:1 CR Notched Pistons
Ported PI Heads CMS Turbo 2Cams Eddy Intake 75mm 60lb inj Twin Cobra Pumps Modified FPDM
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post #6 of 9 Old 03-13-2019, 10:35 PM
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i was having a similar issue and discovered i had 40% and 70% leak down in 2 cylinders

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post #7 of 9 Old 03-14-2019, 05:12 PM Thread Starter
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I had a friend poke around with MAPP gas and found a vacuum leak at the rear of intake plenum. Took the gasket out and just RTV it and short term fuel trims are perfect 1.00. Mapp has definitely best way to find vacuum leak. Leak was small so brake cleaner or starting fluid wasnít working

1999 Mustang GT Convertible
4.75 MMR 750se 10.5:1 CR Notched Pistons
Ported PI Heads CMS Turbo 2Cams Eddy Intake 75mm 60lb inj Twin Cobra Pumps Modified FPDM
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post #8 of 9 Old 03-16-2019, 12:08 PM
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You running a MAP or MAF?
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post #9 of 9 Old 03-16-2019, 12:27 PM Thread Starter
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05 Slot style HPX-E

1999 Mustang GT Convertible
4.75 MMR 750se 10.5:1 CR Notched Pistons
Ported PI Heads CMS Turbo 2Cams Eddy Intake 75mm 60lb inj Twin Cobra Pumps Modified FPDM
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