I don't know if I am to make the maf calculations richer or leaner. As you can see below one side the long term is 118 and the other side the long term is 135. Thanks for any help. The terms are pretty much like this from 2000rpms to 3000rpms. I didn't take it any higher than that yet.

RPM-2600
KPa-43.9
long term-right 118
short term-right 132
long terms-left 135
short term-left 125

 

What 58 mm tb do you have and did you correct the idle air issues most aftermarket tb have?


http://para.noid.org/~lj/PCM%20Tutor...litBLMinfo.htm

 

Tunercat can not resolve split BLMs, you must determine the issue with your motor to fix them properly. Aftermarket throttle bodies as already mentioned, are notorious for them as well exhaust header/manifold leaks at the gasket. Also missfires due to bad plug wires can casue splits too.

 

Tune is not going to do it.
First thing I would look for with a big BLM split is an exhaust leak before the O2 or maybe a vacuum leak.

Then I might try swapping O2s side to side.

I would be looking for things that would cause a false lean be it an intermittently firing plug, exhaust leaks.
Are the injectors new for this setup or did you run them before?

 

just curious, what are the chances of people with bolt ons with similar BLM's that have no clue? No datalogging to see, just a mail order tune.

Makes you wonder how "Serious" it is that they are what they are.

 

As the others who have responded are saying this is more likely a mechanical issue than a tuning one.

118 and 135 are neither too far off the ideal 128 and both signify the pcm is still within it's adjustment range and is bringing the AFR at cruise back to what it believes is 14.7.


If it were a tuning issue MAF tables would also be a really really bad way to try and adjust it.

 

BLMs are funny things and bolt-ons (excluding throttle bodies) normally dont cause splits. I would bet some that have but headers have splits as a result of gasket leaks. Normally the BLMs drop (less than 128) when there is a header gasket leak. Vacuum leaks in front of the TB, tend to make the BLMs go up (More than 128).

The goal is to have 128/128 across the board all the time but that aint gonna happen even on a bone stock never molested engine. Once components like O2 sensors start to age and injectors dont spray as well when new, the BLMs start to split to a very small degree.

When I was fighting bad splits in the past, it was the idle circuit in the BBK throttle body causing it. The idle air was being dumped into the upper plenum of the intake manifold instead of in the original plumbing in the manifold that distributes the idle air to all four intake ports. I also had some plug wires where the conductor had broken free from the terminals on the plug end. IIRC, the splits were very similar to the OP's. When I fixed these issues, mine were 128/128 75% of the time but when they did split is only +/- 2 points. This is very acceptable for a molested engine with heads, cam and all of the other stuff.

The bigger the splits, assuming you dont dip below 108 or above 160, the more the PCM has to lookup parameters in the tables and make fueling corrections to maintain stoichiometric mixture which is 14.7 air fuel ratio. If the BLMs are 128/128, the PCM will not have to work nearly as hard to maintain stoich. Regardless, both of the above conditions would be invisible to the driver in terms of how the motor performs just like GM intended. If the BLMs go over 160 or under 108, you get a SES code indicator and have a significant issue somewhere.

All that said, in my experience, there is almost always a mechanical issue that causes big splits like what the OP is seeing. Agressive aftermarket cams will also normally, cause split BLMs too.

 

I have since upgraded my cam to a 234 244 112lsa and have a 58mm BBK throttle body. For some reason I thought the throttle body would cause splits at only idle but not when I'm actually driving. Glad I asked. I'll let you know if this fixes it. Thanks!

 

Some information you might find useful:
https://ls1tech.com/forums/lt1-lt4-m...htmlnformation