Idle BLM stucked at 123 – need help!

[Marcus]

I did conversion from carburator to TBI some time ago. It´s working almost fine but now I´m trying a fine tune.
The problem is the idle BLM.


As much as I try to adjust the VE table, the BLM reading is always 123. The system goes in a closed loop and INT varies as expected. The reading of O2 swings from 50mv to 850mv. From the smell, it looks like the mixture is rich.
However, when I change to Drive or Reverse, the BLM goes to 128, at the same RPM. When I drive the BLM varies as expected.
I have already tried to increase the injector flow to force Lean and the BLM remains 123. If the INT varies accordingly why not the BLM?


My setup:
Engine 305 standard 50k miles
16197427-$0D BJWN bin mod to 700r4, no EGR, stoich 13.3
TunerProRT, A217 $0D TP5 v250.adx, Advanced $0D TP5 v251.xdf


Can anyone help me with any leads?


Thank you!
Marcus

[steveo]

BLM (block learn mode) may not be enabled all the time in closed loop and is not necessary for closed loop to function. the entire point of the BLM system is to remember trims for later so the adjustments happen more quickly when operating conditions change. your bin may have conditions set that allow closed loop but disable BLM update such as a minimum vehicle speed for BLM to be enabled (so effectively 'trimming' happens at idle but 'learning' does not, and every time you drop to idle, it has to learn all over again). it sounds like that's what's happening here. a lot of GM ecms have a flag in the datastream both for closed loop and BLM so you can tell when learning is disabled.

if the O2 is swinging fairly evenly up and down and the integrator is moving around a bit that means it probably found stoich.

[Marcus]

Thanks Steveo for the information.
Analyzing the TurnerPro log I found that the BLM Update Flag is most of the time, Disable. I searched for BLM Update Parameters and found 'Minimum Temperature for BLM Update Enable' set to 65 centigrade. This seems to me the reason for not working! This temperature may be good for a GM VE table but not for those trying to tune. I'm going to set it to 20 C and test it out.

[LeMarky Dissod]

Thanks Steveo for the information.
Analyzing the TurnerPro log I found that the BLM Update Flag is most of the time, Disable. I searched for BLM Update Parameters and found 'Minimum Temperature for BLM Update Enable' set to 65°c. This seems to me the reason for not working! This temperature may be good for a GM VE table but not for those trying to tune. I'm going to set it to 20°C and test it out.Is that ambient air temp (probably not)? Intake air temp? Coolant temp?
If it's coolant temp (most likely), 60°C seems reasonable. If that does not yield desirable results, try lowering it by 5°C at a time.

[Marcus]

Is that ambient air temp (probably not)? Intake air temp? Coolant temp?
If it's coolant temp (most likely), 60°C seems reasonable. If that does not yield desirable results, try lowering it by 5°C at a time.

I understand that the 'Minimum Temperature for BLM Update Enable' parameter refers to the engine (coolant) temperature. Either way, the problem continues even change to 20 C. The 'BLM Update Flag' remains Disable at idle. I believe that there must be some undocumented parameter. I'll keep investigating ...

[LeMarky Dissod]

Instead of looking for parameters that affect BLM, try looking for parameters that affect idle, like:
RpM
TPS%
MAP
MpH