MAF going crazy after dyno tune.

[02Ls1]

A friend of mine brought me a truck to check it out because they were having trouble shifting to 3rd gear on WOT.

Ok well i took it for a ride and notice that the truck its shifting around 6500 on first to second and 6700 2nd to 3rd, Shifting from 2nd to 3rd the truck bogs down due to the MAF reading way wrong. The MAF parameter on the scanner looks like the Rocky Mountains.

I was on a hurry so i just check it real quick saved the log and the tune. I have study and tune my own cars and close friends cars and trucks and i really like it and i know this truck its tune the wrong way, and it came from what they call a really good tuner with hes shop and dyno. I don't feel like judging someone else work but I'm sharing this so i can see what others say about it.

Truck mods are 5.7, headers, TBSS intake, 3600 converter and 4.10

[pimpin78transams]

I had an issue something similar to this. My maf frequency looks spikey when going wot but everywhere else looks good. Cant seem to get any response whatsoever on this forum. Im starting to lose interest of this site because of this. I don't have too much experience but it looks like your injectors are maxing out as soon as you go wot. Could this be the cause?

[gn2beatu]

Injectors too small - get bigger injectors
Dynamic air disabled - enable it will use a smoother filtered MAF hz (this will help your swings)
PE commanding 13.0 AFR change value to to 12.5
After doing those three things, then re-tweek your MAF/VE tables.

You also have a small amount of knock at 6400 RPM in first log, and again at 6800rpm in 2nd log, tune for ZERO knock, and then subtract an additional degree or two. 28 degrees is allot of timing to be all across the board like it is in both low/high timing tables. Not sure where your located, but if its knocking now in winter, its goona be worse in summer.

Didnt include your config so I cant see what the AFR actually is altho I see it is included in the chart.

[pimpin78transams]

So it is normal for our maf frequency to swing a bit?

[02Ls1]

Will check it this weekend he's bringing it by. I will bring back the dynamic air back to enable. I got this truck like it is and just wanted to see what ya think.

The AFR is in the chart because I was tuning my turbo truck, didn't have a chance and check this truck since I was In a hurry. All my cars that I have before when I go with h/c/I I go on speed density open loop.

One question can I just do another hole on the muffler pipe insert my wideband sensor and start tuning the VE then the MAF but with the o2 sensors active still? I have read before but never try this.

[pimpin78transams]

You can have an extra bung welded in and put the wideband on that bung and leave the o2 sensors plugged in still. Although idk why it would benefit to have them still active. If your tuning with a wideband it should be in open loop and commanding one afr.

[gn2beatu]

Im sure you know this, but put wideband before cats if you have them.

Id recomend against tuning any WOT without a wideband.

I have seen narrow band swings from 780 to 1000mv all at the same AFR.

[pimpin78transams]

Did you mean after the cats?

[gn2beatu]

Yes, pre cat, that was a type and fixed above.