Why is my MAF tuning not working right?

[Fastmax32168]

I am hoping someone can enlighten me as to what the problem is with my current project and getting it tuned correctly.
I have installed a 6.0 with 243 heads and a mild cam into a 91 K1500 pickup.
My initial attempt has been to dial in driveability with the Factory 02 sensors and Long term trims, as it wasn't reading as being too far off when I first fired it up.
I turned off everything MAF and used these factory O2 sensors with a Histogram I created to dial in the main VE table and it runs and drives pretty decent that way.
I then turned off everything MAP related and went to dialing in the MAF sensor.
I created a histogram using Long term trims and MAF sensor Hertz and here is where it went sideways. I want to understand what has gone wrong.
The trims started as under 10 and after a few tuning trips I have them dialed in really close. Most are under 3. But it seems like the closer I got to optimum the worse it runs. It hesitates, pops, bucks, you name it, it just runs badly.
My current plan is to put my wideband on it next and see what the AFR actually is this way, but I am really wanting to understand what I have done wrong here, and why this method did not work, as I have used it before multiple times with no issues.
Thanks,
Roy

[steveo]

lets see your original maf table vs your new corrected one

[Fastmax32168]

lets see your original maf table vs your new corrected one

Thanks for the response. I am really not sure how to accomplish that Steveo. Be happy to try if you want to give me a tutor. I can tell you however that they are not much different. Other than smoothing out a few little wiggles from the original one there is not much changed. It almost looks like two dyno runs from the same motor laid over each other with only very minor differences. Honestly it doesnt run well with either one, although the trims seem to say that it should.
Roy

[Fastmax32168]

Thanks for the response. I am really not sure how to accomplish that Steveo. Be happy to try if you want to give me a tutor. I can tell you however that they are not much different. Other than smoothing out a few little wiggles from the original one there is not much changed. It almost looks like two dyno runs from the same motor laid over each other with only very minor differences. Honestly it doesnt run well with either one, although the trims seem to say that it should.
Roy

let me try attaching the two tune files. maybe something else is screwed up,

[steveo]

can your software graph the table for you
can you post screenshots of both

[Fastmax32168]

can your software graph the table for you
can you post screenshots of both

See if this works

[steveo]

the shape looks okay but the values are odd for just a 10% correction
try selecting all the cells in the table and 'copy' then paste them here, both old and new table
you probably did a massive over correction
how did you do the math per-cell ?

[Fastmax32168]

the shape looks okay but the values are odd for just a 10% correction
try selecting all the cells in the table and 'copy' then paste them here, both old and new table
you probably did a massive over correction
how did you do the math per-cell ?

I let HP tuners do the math. Lets assume your theory is correct, the math was done wrong, and a massive over correction has been done. If that happened I would think my trims would now be way off, not close to perfect. What I really want to understand with my question is how or why the narrowband 02 sensor could be lying to me.
Thanks
Roy

[steveo]

oh okay

im not sure your sensor is lying, but narrowbands lie because:

- they are too cold
- there is wiring damage
- there is interference on the wire (like an arcing plug wire next to the o2 wire)
- there is an exhaust leak before or maybe shortly after sensor
- the sensor has failed due to:
- age
- physical impact
- heavy carbon deposits
- poisioning:
- lead
- silicone
- weird fuels and additives like octane booster

the switching pattern of your o2 sensor (graph the voltage) can be quite revealing regarding whether the sensor is okay or not

[Fastmax32168]

oh okay

im not sure your sensor is lying, but narrowbands lie because:

- they are too cold
- there is wiring damage
- there is interference on the wire (like an arcing plug wire next to the o2 wire)
- there is an exhaust leak before or maybe shortly after sensor
- the sensor has failed due to:
- age
- physical impact
- heavy carbon deposits
- poisioning:
- lead
- silicone
- weird fuels and additives like octane booster

the switching pattern of your o2 sensor (graph the voltage) can be quite revealing regarding whether the sensor is okay or not

Thank you Steveo, I dont think any of those apply but I am going to find out. I will try to get some time this week to set up my wideband on this truck and see if the AFR is actually not what the o2 senors say it is when in MAF mode. Do you have any other suggestions as to why it would run fine on the MAP sensor but run badly on the MAF sensor, both while showing acceptable trims? No trouble codes. Thanks, Roy

[steveo]

i guess the only explanation would be that your trims aren't reflecting reality but that may not be the o2 sensors fault, are you sure the o2s are switching rapidly while in maf closed loop?