o2 placement??

[black dawg]

I have noticed that warmed up good, mostly at low load and rpm, that block learn gets as low as 80. Idle is around 90, and map reads very close to 1 volt. The map voltage looks pretty normal to me, why would block learn be this low. The injectors look good, but do have high miles on them.

if I do get this thing tuned, I would like to have this kinda stuff straightened out first.

If I ever get the chance for you to tune on this mark, would you prefer it was 7747? any particular prom to start with?

[EagleMark]

I'd just tune the ECM and chip that is there. I have most of 1228747 $4F done and a hack so if I needed something it could be added to the mask/XDF.

Feul pressure would be more important to know? Old injectors should really be serviced before a tune, look up Mr Injector.

A scantool is a good tool, but is not a tuning tool. Hard to guess at what is really happening with out data log. But below is an idea of how the ECM handles BLM data and why a cam change or other mods just mess up the way BLM is handled.

Minimum BLM for ARPA is 84. So your maxed out for taking away fuel. The reason this happens is the engine design has changed, cam mostly so idle MAP kpa of stock engine is about 30-35 and with a cam and stock chip it's probably 60-65 MAP kpa. So the ECM thinks there's a load and add's fuel! When in Closed Loop the O2 sensor is trying to correct but can only correct to 84 BLM. If the fueling table was correct it would be 128. Being this far off in a wet intake manifold is just horrible for any consistency of idle for a rock crawler.

There are other issues with CL and cam using learned BLM. Here's what the BLM Learn table looks like stock. With a cam changing MAP well then you get idle BLM in the 8-9-10-11 row along with driving!!! So you really can't even use BLM data for tuning unless you use a spreadsheet or strip out idle and driving to adjust VE fueling tables.

;---------------------------------------------
;
; _______|______|_______|______
; | | |
; 12 | 13 | 14 | 15
; _______|______|_______|______ HI MAP 81 Kpa
; | | |
; 8 | 9 | 10 | 11
; _______|______|_______|______ MID MAP 58 Kpa
; | | |
; 4 | 5 | 6 | 7
; _______|______|_______|______ LO MAP 18 Kpa
; | | |
; 0 | 1 | 2 | 3
; _______|______|_______|______
; | | |
; 750 LO RPM ______| | |
; | |
; 1800 MID RPM _____________| |
; |
; 2600 HI RPM _____________________|

Here's some of the BLM Min Max to show where I got 84 Min value.

LD2B1 FCB 0 ; BLM IDLE CELL INDEX
LD2B2 FCB 1 ; BLM MODIFIER
;
LD2B3 FCB 172 ; MAX BLM VALUE
LD2B4 FCB 84 ; MIN BLM VALUE
;
LD2B5 FCB 134 ; MAX BLM AT INIT
LD2B6 FCB 122 ; MIN BLM AT INIT
;--------------------------------------------
*****************************************
* BLM RELATED
* ARPA, TYPE $4F ECM
*
*****************************************
LD2A2: FCB 147 ; STOCH AFR
;
LD2A3: FCB 12 ; FREQ OF BLK LEARN UPDATE, (0.54 SEC)
;
;

Below is how you change the BLM Learn table to you new engine design so you can have idle, drivng and high load all come out in right areas of BLM Learn like a stock motor would, then when driving the BLM will be in order and not have to do massive correction because idle and light cruise are in same cells as load.

LD2A4 FCB 36 ; RPM, BLM RPM CELL BOUNDRY
LD2A5 FCB 88 ; RPM, BLM RPM CELL BOUNDRY
LD2A6 FCB 128 ; RPM, BLM RPM CELL BOUNDRY
;
LD2A7 FCB 20 ; BLM MAP cell boundry
LD2A8 FCB 112 ; BLM MAP cell boundry
LD2A9 FCB 192 ; BLM MAP cell boundry
;
LD2AA FCB 3 ; BLM cell RPM Hyst
LD2AB FCB 8 ; BLM cell LOAD Hyst

[black dawg]

Fuel pressure is 13 psi. The part that seems strange to me is that map voltage at idle is 1v. Not sure how that translates to map kpa, but my stock tbi 350 burb shows map slightly over 1v.

Block learn does go up some as load/rpm is increased, but never goes over 120.

[ony]

proble got a bit more vaccum on it than your other one, proble around 30-32 kpa.

[EagleMark]

MAP Voltage of 1 volt = MAP Kpa of 30 and vacuum of 20.

You said a mild build but never gave cam specs? Aftermarket cams are always lower idle MAP kpa.

[black dawg]

cam is
stock 454 vortec
204/209 @ .050
.480 .483
118 lsa

heads are early large ovals on stock mid seventies short block.
Used the vortec cam to get away from lobe/lifter issues.

seems to me that either this stock tune is pretty rich, or extra fuel is being delivered somehow.

[EagleMark]

The cam is not big and idle MAP of 30 is not bad. But you have changed the design of the engine without changing how it is calibrated, so yes it's off. It's not that the stock tune is rich, it's you changed the engine! There are spark and fueling changes needed to see the changes you made.

EFI is forgiving and can make adjustments so lots of changes will run. But it can only do so much adjustment, it's calibrated to do one thing, can't expect it to do another.

Biggest issue is you BLM is at 84 which is max removal of fuel to keep up and it's not enough, running that rich all the time washs oil out of cylinders and rings wear. With your cam and idle MAP kpa I don't expect it to happen fast. But if you sniff your dipstick and it smells like gas? Well it's happening.