Tip in backfires/"pops"
 

Hey guys! Would love to brainstorm a lil on a new issue that popped up when my tuner ported my tune over to a new ecutek update/Racerom version.

If I ever so gently tip into the throttle while cruising I'll get rapid fire backfires or pops in my header and exhaust. Logs show no knock or misfire counts.

It will happen on certain downshifts too.

Any idea what this could be?

I have 0 cats and no exhaust leaks. It goes away if I flash back to previous rom version.

lean miss-fire is my guess, despite not having a miss-fire count in the ecu. Either that or a column got transposed somewhere. Do you have a wideband?

Yes I do. I can post a log

Yeah You need to find out if it is too lean or too rich when this happens. Also log ignition timing to see what it is doing. Which ROM cal id did he switch from and to? Have you brought this up with your tuner yet? It maybe just one of those small details that got transposed when moving his tuned changes to a new ROM cal id.

@mad_sb

Here is accelerator position vs. Wideband (custom map O) vs. AFR

https://fbcdn-sphotos-f-a.akamaihd.n...52662789_o.jpg

Here is accelerator position vs. Wideband (custom map O)

https://scontent-b-ord.xx.fbcdn.net/...86019376_o.jpg

Here is accelerator position vs. Timing

https://scontent-a-ord.xx.fbcdn.net/...02413126_o.jpg

Thanks for any insights!

OK, If i am reading the graphs correctly, and i may not be..

[edit after staring at the graphs some more]
Yeah that is lean misfire, look like the fuel just shuts off as you tip in. I once tried to set the main fuel map leaner than 14.7 in the cruise area, it would do just the opposite, when you saved the file it would go full rich in that cell as leaner than 14.7 is not supported in the rom. and it would go into heavy missfire when you hit that cell.... I did not log it as i had full access to the map (brzedit at the time) and saw it the instant i opened the map file again.


I have seen my own tune go sideways as a result of porting it to a different stock rom (a00c to a01c). All sorts of weird behaviors, so I went back to and have stuck with a00c. My bet is it is 100% an issue with a setting in the tune or an incompatibility in the new base tune file.

Timing looks ok, fuel is just not there on tip in. I would send those logs to your tuner and ask them to double check all the settings. So many possibilities it may be easier for them to just start over and try again.

The fuel AFR looks normal to me. If there wasn't enough accelerator enrichment you would see a lean spike in both AFR right after throttle tip in and then it would level out. Log requested AFR and what are you fuel trims doing?

@sw20kosh

Help me understand what I am looking at on the first log graph you posted.

Lets look at the tipin event right after 2.0 mark on the x Axis:
To me it looks like you tipped in from zero accelerator angle to about 4.5%
At the peak on the tip-in event it looks like the factory front 02 is reading 20:1 or dead lean? Or is the scale not the same for afr as it is for accelerator pedal angle? Also looks like the wideband is further down the pipe and offset from the factory sensor but it is also reading dead lean at the peak of the tip-in?