Ebl flash 2 4.3 700r4, what are the potential causes of a reported BLM of 108 while the wideband is reporting 20:1. Only happens at very light throttle cruise conditions, while in closed loop. Narrowband O2 sensor is reading almost zero volts, but the pcm is still trying to pull fuel. If I force open loop it runs like a dream.

 

Are the two sensors on the same side of the engine?

 

Yes, they are, about 6" apart. The wideband is before the narrowband 2" rear of the merge in the y pipe, full new system no leaks.

 

If you've pegged the BLM at 108, my suspicion is it would probably go lower if it could (but I think 108 is the lower bound in the calibration).

So what may be happening is one or more cylinders want to run rich, causing the ECM to want to pull fuel out. The 108 is the indication that the ECM is leaning out the mixture to try to compensate for that, which means every other cylinder is probably lean (or possibly very lean), generating the overall 20:1 AFR on the WB and the ~0V on the NB.

Probably run through the standard checks of the spark plugs and wires, injectors, etc. It could be one cylinder "misbehaving" and causing the ECM to "punish" the other seven cylinders. Remember, it's batch fire, so no individual control of fuel mixture on a per-cylinder basis... it's all or nothing.

 

Anything below a 128 blm is rich correct? So that would be showing as extremely rich,oddly enough the int stays at 128. It will only do it in closed loop cruise, if I twitch my toe on the gas pedal (I dont even have to go far enough to hit ae) it immediatly returns to 14:1 accelerates properly and will not go back to the superlean condition until its back at an almost zero load condition. Ae makes it go rich as it should, pe makes it go rich as it should. Just kinda confused as to what I did to cause this. (New msd distributor, cap, msd 6 ignitionbox, rotor, coil and wires, new ngk plugs. New redtop 33lb/hr injectors (everything above the heads is new)

 

I'm confused now...

You initially said "at very light throttle cruise conditions, while in closed loop".

But you're saying now "It will only do it in open loop cruise".

Is it open loop or closed loop?

 

Sorry in open loop it behaves as it should, when in closed loop and the pcm is adjusting the pulsewidth is where I am experiencing issues. The part that confused me the most
blm was 108
int was 128
O2 mb was .13mv
Afr was 19.6:1
My interpretation of this data was that long-term fuel trim (blm) was at 108 short term was 128 short term showed stoich (int) the ebl could see that it was extremely lean (.13mv) but it was still pulling fuel, to yhe point it went all the way into async. I'll do a datalog after work and see what it shows I could post it up if it would help. I could also post the tune file.

 

BLM of 108 in closed loop means the ECM has been pulling fuel out of the mixture over the "long term".

I wonder if you're entering into some sort of highway mode fueling. I'm not exactly sure how the EBL works in this regard.

But in my $8D code, after about 10 seconds of crusing at light throttle above a certain speed (I have it set to 55 mph), highway mode fueling will kick in. IIRC when my highway mode kicks in the INT will lock to 128 (indicating it's in a quasi-open loop mode) and then the ECM will work to the pre-programmed AFR I put into the calibration. I have my AFR set to produce a 16:1 AFR on the WB and the NB will be down around ~100 mV.

But the BLM will remain at the value that it was at the time highway mode was entered. As soon as I give it a little throttle, it exits highway mode and goes back into closed loop.

Unless you're datalog is in Tunerpro, I won't be able to view it. And I don't have the EBL so I can't look at your tune. Maybe someone else on the board can.

 

I use tunerpro Pro and I can send you the xdf file. I'm pretty sure I disabled Highway mode by setting the coolant temp sensor enable threshold to 151 Celsius but I will verify.

 

I think it would be in the bin file not the xdf?

 

Ebl files need a specific xdf in order to read them with tunerpro. Laptop died before I left work so tomorrow I'll have to get the datalog and grab both the bin file and the xdf then I can upload them.