Lean issue - Ford Mustang Forums : Corral.net Mustang Forum
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post #1 of 6 Old 03-12-2019, 06:07 PM Thread Starter
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Lean issue FIXED!!!

I am having a problem tuning my car. When I datalog it my STFT are perfect on passenger side bank1 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. I am tuning with sct pro racer and datalogging with live wire

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 6 Old 03-12-2019, 07:06 PM
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intake gaskets on that bank are leaking

When cold, spray water, a good stream of it, around that side and listen for hissing

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89 GT gr-40, KB2200(10psi), tweecer R/T,LC-1, 22gal cell, w/tailpipes.
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post #3 of 6 Old 03-12-2019, 07:10 PM Thread Starter
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I sprayed soo much brake cleaner to see if it was the intake that I ruined all my powdercoat no reving of engine at all

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 6 Old 03-12-2019, 08:19 PM
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what are you talking about?

spray water and listen

if you sprayed brake clean you should have been looking a short term fuel trims, not engine speed.

89 GT gr-40, KB2200(10psi), tweecer R/T,LC-1, 22gal cell, w/tailpipes.
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post #5 of 6 Old 03-14-2019, 03:55 PM Thread Starter
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Quote:
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what are you talking about?

spray water and listen

if you sprayed brake clean you should have been looking a short term fuel trims, not engine speed.

So I sprayed the water as suggested and couldnít find anything. I had a friend poke around with MAPP gas and found a vacuum leak at the rear ok intake plenum. Took the gasket out and just RTV it and short term fuel trims are perfect 1.00. O2 volts are off from bank to bank is that normal?
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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 6 Old 03-14-2019, 07:29 PM
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what are long term trims?

your 02s should have a min of near 0 and a max near 1 and should be cycling continuously

one of your sensors looks like it is fixed rich, high voltage

89 GT gr-40, KB2200(10psi), tweecer R/T,LC-1, 22gal cell, w/tailpipes.
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