Low Int and BLM

[Sammy_Johns]

In CL I seem to have low Int and BLM. I graphed my O2S output and it seems as though it will not get down to .1 Volt very often. I had read that swing between .8 and .1 was necessary for proper operation on a GM O2S and it should be at least 600*. O2S was replaced a while ago (Delco). Maybe more importantly I seem like it takes a long time to get into CL. I usually have to actually start driving to get it in CL. Temp around O2S bung is around 425*F. Even the exhaust man. is only in the mid 500* and I have to be in the throttle to get it even that hot. It's 80* outside today. So seems like it may be a good idea to put in a heated O2S and see if that buys me anything. However, if my Int is low (lean) isn't my BLM suppose to use that data to lengthen the pulse width of the injector to richen it up and bring the BLM closer to midpoint (128)? My logs always show low int and BLM. There are map errors in my xls, but I was testing my MAP with a vacuum gun. Map seems to move ~1V per 5 in.Hg. It's been a year or so since I checked, but fuel pressure was 12-13psi. New diaphragm in the Fuel Pressure Reg. at that time and I compressed the spring as far as I could to get that. Any feedback or suggestions would be appreciated.

[lionelhutz]

The O2 doesn't have to specifically swing down to 0.1V. It just has to be crossing 0.45V which is caused by the control loop slightly oscillating the fuel back and forth around stoichiometric.

Running a heated O2 sensor is a very good idea unless your O2 sensor is right in a factory manifold or at the down pipe connection of a factory manifold.

The BLM will not return back to 128. It is a long term fuel correction. If your log hits one cell multiple times and you find the BLM in that cell is either higher or lower than 128 then it is indicating the tuning is either lean or rich in that area. Take any areas with high BLM values and pull the VE table up to a higher number. Do the opposite for areas with low BLM numbers. Manually look at the 3D map and make sure any transitions are fairly smooth. Start by changing the VE table about 1% for every 2-3 counts the BLM is away from 128 and see how it works.