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Author Topic: Could I be getting a false lean?  (Read 1061 times)
dorton
EMS Poster Child
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Posts: 6
« on: April 21, 2008, 08:26:55 AM »
My setup is an 86 mercury capri, w/stock heads,cam, and short block I have 42lb injectors, and a single gt4088 turbo. Untill a week ago, I had been running the stock intake, and throttle body and it was running great. I have just added a trick flow track heat intake, and accufab 70mm tb. I immediately noticed the car running lean after install. I richened the fuel trim and it still stayed leaner than what I wanted. I turned the fuel psi up and rolled into the throttle, it did not feel right, so I let out. The a/f was around 13.5(still too lean)and when I let off the throttle, it felt like the pedal kicked back?!!?
In trying to make sure nothing popped during tuning I had  backed the timing on down.
It just puzzles me that it ran so good before, and now I'm not sure where to start next?

Could too much fuel, and not enough timing be causing a false lean?

Any help would be appreciated.
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dorton
EMS Poster Child
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Posts: 6
« Reply #1 on: April 25, 2008, 05:07:52 AM »
update:
I dropped fuel pressure 5lbs and gained 1 full point richness a/f. The car felt much better,
but then still would not richen any more. Now, my theory is my alternator is on the way out causing low voltage and making my WBo2 read off.
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ziptie007
25+ Posts Club
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Posts: 63


1987 yellow notch, pdp s3 turbo kit


WWW
« Reply #2 on: June 10, 2008, 03:31:30 AM »
nice to see another turbo mustang on here. When I think my wideband may be reading wrong I do the old school thing of pulling a plug and looking at the color. Thats what I did back in the day before I even had a wideband. Tan is allways the best color. White is lean and sooty/dark is rich. Hope that may help some.
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yellow notch with black interior
pony down performance stage 3 turbo kit
paul anthony built 331
jeff carroll (lol me) built c4
9.75 @ 139 with pump gas and 16psi
r.barn
100+ Post Club
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Posts: 172
« Reply #3 on: June 11, 2008, 04:39:44 AM »
Quote from: dorton on April 25, 2008, 05:07:52 AM
update:
I dropped fuel pressure 5lbs and gained 1 full point richness a/f. The car felt much better,
but then still would not richen any more. Now, my theory is my alternator is on the way out causing low voltage and making my WBo2 read off.

Voltage offset is very important for injector firing.
If your electrical system is weak or poorly grounded it can cause problems.

I would upgrade all your grounds too.
Battery to Frame
Battery to Engine block
Engine block to Frame
Heads to Frame
ect. ect. ect.

you cant have too many grounds, IMO


Here's a nice pic of data logging I did on system voltages
before and after ground upgrade when I was having issues once.

Before


After
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'89 5.0 LX-Vert, 351W roller, RHS200's, LSM custom turbo cam,
SuperVictor EFI intake,  4 brl TB, AEM .... Twin 60mm turbos coming
smc_customs
25+ Posts Club
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Posts: 27
« Reply #4 on: June 29, 2008, 08:11:33 PM »
damn thats a huge difference
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