Wierd AFR while cruising

[ovenroastedlnf]

Car: 2007 Cobalt SS/SC
Mods: intake, ls4 tb, pnp sc, h/e, 2.8 pulley, 60's, catless dp & exhaust

While tuning in open loop the car runs fantastic, perfect afr all around!

When put in closed loop, the trims were a bit off still. So we did a few logs and tuned them down. While cruising around the gauge will randomly go into the 17's and just stay there. He has to give it some gas, not quite full throttle, but peg it real quick to get it to go back to normal. I figured it was just the full trims needing adjustment. So we just kept adjusting and eventually the trims were fairly close, didnt finish due to getting late and he needed to leave, but still within 2-3%.

When looking at the logs, his trims are in the negatives which would mean he is running rich, but the gauge is showing it running in the 17's at some point...

When we first met up, his car was wistle to it, sounded turbo'd actually. I think it is an exhaust leak, but he said he thinks its his tranny. What do you guys think could be the issue? If it is in fact an exhaust leak, then I think fixing that will solve our issue. I am at work now, I will post the tune and my last couple logs up when I get home.

[Speedytec]

The LSJ sometimes runs O2 tests where the reading is richer than stoch, but during this test the normally fluctuating STFT switches off.
If the narrowband/STFT switching is unchanged during these 17AFR moments, something else (WB reading) is wrong.

[ovenroastedlnf]

Here are some of the logs and the tune.

It does it a couple times, once it is down to 12.8, which I would guess is the cat test, and it also does it at 17-18 but I dont know why it would be doing that...

[ovenroastedlnf]

Heres the config I am using if it helps.

[Speedytec]

Not sure on you current config file, but try a log that includes Commanded AFR. You'll see that commanded AFR switches to ~16,3 and STFT's switch off. This is an O2 sensor and/or CAT test the ecu runs and your catless DP is probably causing this. The 2007 ecu's are a bit sensitive on this (ask Area47), so fit a DP with sportcat or maybe it's enough to fit an 2nd O2-sensor cheater.
Let us know the result.

[Area47]

put the rear o2 code to no mil, and put it back in the stream. set the cat code to no mil as well.

[ovenroastedlnf]

I have the commanded afr logged in the primary table, just not showing in the gauge. Is there a way to delete this test from happening? I think I have all the 2nd o2 codes deleted so I dont know why it would still be checking for them..

[ovenroastedlnf]

OK thanks Area, Ill try that.

[ovenroastedlnf]

Set the codes back to what you said Area, still going lean randomly..

[GM COBALT SC SS]

Set the codes back to what you said Area, still going lean randomly..

maybe oversight, but did you reinstall the 02 as well?

what kind of wideband? my ngk afx was running really weird numbers until i actually calibrated it correctly. i know its trivial, but just thought id throw that out there

[ovenroastedlnf]

Ya the rear o2 is still installed and it is a AEM uego wideband.

[laser_racer]

Not sure if you notice this or not but the car is in open loop so I can see where weird afr might come from. Also the iat2 is really high and some more sensors on the config.

[ovenroastedlnf]

So its going into OL when its leans out and the fuel trims shut off for those random few seconds? If so, how do I prevent that?

[laser_racer]

Well thats hard to say really. I did notice your not logging front o2, injectors, or throttle position. It looks like your logging the throttle in the car just not the throttle body. You might need to start with the stock tune and start over.

[cobaltssoverbooster]

questions:
why are you running a 100% maf tune?
you should be ve till about 1500 at the lowest then go maf tune. ve is more accurate and i see way better idle on modified injectors when ve is done properly.

Did you know you have factory closed loop enable factors?
This is why you go in and out of closed loop. (just a reminder- open loop = no 02 sens and closed = o2 sens reporting)
if you are going to tune ve which is recommended by everyone on here then you need to raise your closed loop enable tables to the maximum values so the oxygen sensor doesnt have any say.

Why do you need a pe tps value at 20%?
set it higher to like 80%.... then record a log where you are in third gear right around 2800 rpm and push the pedal down multiple times increasing the depth of the initial hit to see what tps value nets an average of 2-3 psi then set it for that tps value. then increase the rpm and do it again. a log when done properly should shift out of stoich under 3 psi boost. the alternate way would be to drive it and make a histogram with tps percentages in 5% increments starting from 40 to 100 and set the data loaded as boost in psi. where it averages 2-3 set pe tps to that value across the board and just scew pe accordingly.

raise the fuel pe enrichment rate to a value of 2.0 and leave it. this will ramp the rate at which you hit pe from stoich values. i.e. the slope is shorter so you get to commanded pe faster.

Why is your pe delay at 2200rpm?
i would recommend raising it to 2800 - 3000 so you can utilize the heat from a leaner ratio down low where the motor is bogged and loaded anyways. if your hitting pe under 2600 your either trying to get out of crashing during cruising or you need to revise your driving habbits a little. Heavy load on the motor at low rpm is not recommended. ask any engine shop.

max boost 1st and 2nd gear has values of 200%? you do know the tables maximum value is 100% right?
anything over that will have no effect

factory maf fail high value with a 2.8 pulley?
most people pop codes because they went to the 2.8 and didnt raise this value to the max when they were using their maf. if you go to ve tune though make sure u set it 0 before you tune in ve mode.


sorry to tear it up but from working on the lnf which from experience has the worst consistency rate, some of the corrections here will bring your logged consistency rate up and get rid of some of the problems you have run into.

[laser_racer]

Well with the 20% pe setting that would make since why they the trims kick on and off.