Freescan is so cool!!

[TraceZ]

Wow, nice readings. If you don't mind, could you share some under normal cruising and/or possibly WOT, if you ever do that?

Sure. As soon as I get a chance to drive it again with the laptop hooked up I'll post them. Man, this car feels great. I really missed it over the winter.

[Craig 94 TA GT]

Thanks Tracy
I'm impressed with your BLMs and pulse widths. Mine are higher than yours at a lower idle (4/3 at 550 idle) and I'm curious to see yours under any throttle. I have a higher air flow rate at lower idle too, which is kinda funny...maybe my MAF is off. Either way, I'm excited too see it and we can make sure yours is 100% everwhere

[TraceZ]

Thanks Tracy
I'm impressed with your BLMs and pulse widths. Mine are higher than yours at a lower idle (4/3 at 550 idle) and I'm curious to see yours under any throttle. I have a higher air flow rate at lower idle too, which is kinda funny...maybe my MAF is off. Either way, I'm excited too see it and we can make sure yours is 100% everwhere

Do you have the screen in your MAF? Mine is fully intact. I've been told that removing the screen can throw off the calibration of the sensor.

[Craig 94 TA GT]

Do you have the screen in your MAF? Mine is fully intact. I've been told that removing the screen can throw off the calibration of the sensor.

Yea, bone stock. I had a MBA ends on before but switched it back. That may have screwed it up for good. I'm reading 7-8 gps at 550 idle, 280-290 at peak RPM WOT. PWs are around 20-21 at 4800 to redline, 90-93% duty cycle. Yours PWs and GPS air readings seem right on par with what it's supposed to be...at least for idle

[wrd1972]

What are BLM's and what are the correct BLM's to expect?

[Injuneer]

What are BLM's and what are the correct BLM's to expect?

Read the "air/fuel management" section of my scanner guide.

Basically, its a "block learn multiplier"..... a number that is used to correct the PCM's fuel calculations, if the O2 sensors indicated the engine is running rich or lean. The "multiplier" is expressed as a number between 0 and 255 that is used to develop a correction multiplier. A BLM of "128" means the PCM's standard fuel calclation is multiplied by the factor of 128 / 128 = 1.00. In effect, "128" means no correction is required the multiplier is "1". In OBD-I, the terminology is generally as an absolute number..... e.g. BLM = 128. In OBD-II, the scanner will often show the BLM as a "%".

If the engine was running lean, the PCM would start increasing the BLM to get the A/F ratio back to 14.7:1 where is has to be for decent fuel economy and and minimum emissions. With a lean condition, the PCM might increase the BLM to say 135, and the resulting correction factor would be 135 / 128 = 1.0547. In that case, the computer would be adding 5.47% extra fuel to its calculated fuel flow, and increasing the injector pulse width to get the extra flow.

BLM's are also called "long term fuel corrections" because the PCM "learns" them and stores them for future use. There is also an identical "short term fuel correction", also called the "integrator" that is used to make temporary corrections, as the PCM intentionally dithers the operating conditions back and forth between very slightly rich and very slightly lean. The cat convertor needs this dithering to store O2 when it breaks down NOx, and to then use that stored O2 to oxidized unburned HC's and CO to CO2 and water.

To further complicate it, there are 18 different "cells", each with its own stored BLM, one for the right bank and one for the left bank. The "cells" are defined by a 4x4 grid of RPM on one axis and engnie load (MAP) on the other. In addition to the grid there is a cell for idle (#16), one for open loop load (#18) and one for decel (#17).

You want the BLM's to be close to 128 (0%). That means the engine is operating at the correct A/F ratio, within the parameters of the stock PCM programming. A variation of +/-5% is generaly acceptable (122-134). And, you want the left and right ranks of the engine within a range of +/-2 counts. Any larger deviation tells you something is affecting one side of the engine and not the other.

The BLM's have limits.... they can not go below 108 (15% reduction in fuel) or over 160 (20% addition to fuel). When they reach those limits, you will get a code for "rich" or "lean".