Open loop tune done, CL is a mess

[CLRD4TO]

A couple days ago I finished street tuning. My tune from last year was ok but not perfect. Now I swapped injectors and did full exhaust, so I touched up VE. OL AFR error was less than 2% in normal drivability range. With the table copied in to the stock form closed loop (LTFT and DFCO enabled) the car now drives like shit. It gets worse the longer I drive it since the last flash. WB drifts way lean at times during normal driving and nearly stalls approaching stops. Im tempted to disable LTFT if not closed loop entirely.

The attached scan file recorded the MIL tripping on, fault is lazy B1S1 o2. I know majority of scan is limp mode but the afr drifting baffles me.

Thanks for input.

[WS6FirebirdTA00]

I always disable LTFT and only keep STFT. Did you tune the o2 sensors after the exhaust change? How new are they?

[CLRD4TO]

I don't know how to tune the o2's. Both were replaced last year. I'm worried that I zapped the left o2 with the welder. I was in a rush and didn't bother removing them.

Drove it to work today with forced OL and drove great. I think I will keep LTFT disabled. Should I also disable idle ltft?

[WS6FirebirdTA00]

disabling the LTFT does not mean you are in OL. You have to put it in OL. STFTs are still active if you just disable LTFT.

[CLRD4TO]

I flashed it this morning with cl enable at max temp.

[domestic rice]

Yeah man I feel your pain. I had my MAF and Ve all dialed in, then when I enabled my STFT's it all went to crap. The STFT's say rich, the WB says lean and car runs like crap, stalls ect.... I just disabled the fuel trims set the ECT to 285 and run it like that. runs much better that way until I can figure out the deal.

[WS6FirebirdTA00]

Just need to dial in your o2 switch points and ensure the proportional fueling is set for proper switching. Other than that your o2s can be bad.

[motorheadmike]

Just need to dial in your o2 switch points and ensure the proportional fueling is set for proper switching. Other than that your o2s can be bad.

Can you please elaborate on this?

Thanks.

[gokussx4]

Can you please elaborate on this?

Thanks.

Fuel > Open & Closed Loop > O2 Rich/Lean vs. Airflow - Bank 1 and Bank 2

You will want to compare the airflow mode numbers to your General - Mode vs. Airflow table but here you can see that most of the cruising area is set at 16.

My understanding is that, while in closed loop, the pcm will try to adjust fuel - or + based on the settings in the 2 bank tables.

So for example, if you are driving down the road and your airflow mode is 16 and the value for that airflow mode's switchpoint is 601 (bank 1 table stock for a 2000 ls1) then it will start adjust fuel as it crosses 601 mv.

Please someone step in and correct me if my understanding is incorrect.

Hope this helps!

[CLRD4TO]

Yeah man I feel your pain. I had my MAF and Ve all dialed in, then when I enabled my STFT's it all went to crap. The STFT's say rich, the WB says lean and car runs like crap, stalls ect.... I just disabled the fuel trims set the ECT to 285 and run it like that. runs much better that way until I can figure out the deal.

I started this thread when I had problems with my green tops, turned out it was low pulse width problems. It was a huge headache but did get them tuned right.

Sounds like your problem is needing to tune your O2's as described above.

[WS6FirebirdTA00]

Also your proportional fueling. That adjusts the frequency of the o2 oscillation. If you add too much you can flat line high or low, too low it will hover around your commanded AFR and not move. You want quick oscillations and then set the switch points so they float around your commanded AFR. If you tuned with the WB and put it in CL, you can build a histogram to plow STFT error (disable LTFTs) vs airflow (which correlates to the airflow mode table). Then you can see if you need to adjust the switch points higher or lower. Bottom line is when it is tuned off the WB the STFT error should average out close to zero.

Believe it or not, I pulled some original 2000 o2 sensors from the attic for my car to just try closed loop out again. They are still in the car and working great. A lot of times o2 sensors are replaced after a setup change and the real issue is the setup not getting the proper fuel trim oscillation.

[gokussx4]

Also your proportional fueling. That adjusts the frequency of the o2 oscillation. If you add too much you can flat line high or low, too low it will hover around your commanded AFR and not move. You want quick oscillations and then set the switch points so they float around your commanded AFR. If you tuned with the WB and put it in CL, you can build a histogram to plow STFT error (disable LTFTs) vs airflow (which correlates to the airflow mode table). Then you can see if you need to adjust the switch points higher or lower. Bottom line is when it is tuned off the WB the STFT error should average out close to zero.

Believe it or not, I pulled some original 2000 o2 sensors from the attic for my car to just try closed loop out again. They are still in the car and working great. A lot of times o2 sensors are replaced after a setup change and the real issue is the setup not getting the proper fuel trim oscillation.

This is great advice! I am just getting to that part myself and this really helps!

[oakley6575]

Old thread but WS6Firebird, can you explain on how to set up the histogram. I can't find an airflow mode table to log.

[WS6FirebirdTA00]

You have to set up airflow mode manually. Look in your tune and find what airflow relates to a certain airflow mode. Use that to manually set the axis.

[02Ls1]

I know this is an old thread but just wondering why not just leave it i Open Loop.