A little too simple

[Fran and Bud]

I see that others have noted the 4.3 injectors as the source of the lean
condition. By the way, the color code for the 4.3 is Yellow/Blue.  

As to bore size, I have other throttle bodies with the same size bores as in
my 93 PU 4.3.  According to the Production Numbers on the others they are
for 5.0 and 5.7. I have also been told by others that
they all have the same bore size.

And since injector size is at the center of this post, it brings to mind
another piece of trivia that I have been told BUT KNOW ABSOLUTELY NOTHING
ABOUT - that the code in GM ECU's includes an address that contains an
"injector factor" that is used in conjunction with the mapped data, and
which needs to be adjusted when different sized injectors are installed.  
Can someone elaborate??

If this is the case then should Bill try to find out exactly what was in the
Caprice and use that size so that the ECU will match without changing
anything? - OR is this down in the "mud level" of details?
 
----------
>From: Onebil2mny at aol.com
>To: DIY_EFI at efi332.eng.ohio-state.edu
>Subject: A little too simple
>Date: Sat, Feb 6, 1999, 5:44 PM
>

>First, I would like to introduce my self..  I'm Bill, and I'm a caraholic.
>
>I am currently working on a 56 BelAir conv with a production line LT4 using a
>GM ECM from Howell, 700R4 tranny, and all kinds of other non list related
>mods.   I am also building (for my self, the BelAir is for my Father) a 72 442
>conv. LS-6 crate motor with a Roller Hydraulic cam, Wiand Team G with injector
>bungs, Kinsler throttle plate and an Accel ECM. It also has several dozen non
>list type mods. I think this list may be a little advanced for me, as I'm only
>an ASE Master Tech, and don't have a Bachelors degree in anything.  I've been
>following a couple of the posts lately, and I don't know a thing about burning
>proms, much less building a device to modify OBD2 ECMs!
>
>Anyhow, here is my query.....   I have installed a TBI motor from a 91 Chevy
>Truck in to a 85 MonteCarlo.  The Monte was originally equipped with a TBI
>4.3L.  I have installed a 91 Caprice ECM & Prom (ECM service # 16136965) and
>on the monitor everything seems OK, except for the MAT as the Monte was not
>originally equipped with one.  I will install on soon as I have the pin outs,
>sensor and sensor pig tail....  I just need the terminal at the ECM.  My
>problem is what appears to be a terrible lean condition.  I am using the 4.3's
>throttle body as I was advised it should keep up.  It does appear to have the
>same size throttle bores, and I can only assume injectors are ok....  at least
>for Idle!  Anyhow, I have checked for the obvious, vacuum leaks, etc. but it
>still runs lean, hesitates, backfires, etc.  That is until I dead head the
>fuel pressure.   If I pinch off the return line, it runs fine.  I have 12 psi
>at idle, in spec for a 85 car, but I don't know the proper pressure for a 91.
>Could low pressure be my problem?  Does a 91 Caprice TBI require a higher fuel
>pressure?  Or, is there something wrong with my choice of ECMs?  Any
>suggestions would be great!
>
>
>Thanks for the help. and sorry if this is a little too simple.
>Bill (feels so uneducated) K