Wide band causing open loop issues

[ChaseJ]

I am starting to tune my 1998 K2500 with a 350 in it. The motor is bone stock other than a K&N intake from the previous owner and roller tipped rockers in the stock ratio. The motor has a couple thousand miles since I rebuilt it. All of the sensors were replaced and the truck runs great, other than it gets bad gas mileage. However, it does have 4.11's in the rear, so it is kind of expected.

After some tinkering in the software, I have all of the tables and graphs set up to tune(or at least I think so. Still trying to figure this stuff out). My wide band O2 sensor is also set up and displaying in the software. The wide band is installed in place of the stock driver side O2 sensor.

I went into the stock program and forced the truck into open loop in order to data log and start tuning. I also changed the power enrichment to 0 second delay. (For future wide-open throttle tuning). The truck ran like crap. It had a very hard time getting up to speed and was way different than normal. Air-fuel ratios were 14.5 at idle and 19-20 at normal driving speeds (35 mph). It drove so terrible, I turned around and went back home. I thought I probably messed up something, so I reflashed the stock tune, which is not forced open loop. Wide band O2 was still installed. Same thing happened. The truck ran terrible and had an air-fuel ratio right around 20 when driving in town. I uninstalled my wide band and put the stock narrow band O2 sensor back in. The tune was not changed at all. Runs like a millions bucks. The problem seems to be the wide band O2 sensor. The check engine light did not come on and there were no error codes when I checked.

Can anyone explain why a missing driver side O2 sensor would affect the truck when it is forced open loop? As I understand it (Correct me if I am wrong), the truck should not look at the O2 sensor's at all in open loop. It would only use the O2's in closed loop. My log and tune files are attached. Log file is in open loop. I did not do a data log with closed loop enabled. Is there some other issue I am simply over looking? Did I not force open loop in the right way? Am I just a poor boy from a poor family??? Spare me my tune from this monstrosity. Any help with this would be greatly appreciated because this baffles me to no end.

[Oleblu]

You should add cylinder air mass to your channels list. You forced the truck in open loop but left the fueling dynamic. Using both the VE and the MAF. it was still using both airflow models for fueling calculations. Im not very versed in the black box computers from these trucks as I have 0411 pcm swapped mine. But the proper way to force this black box computer into open loop SD would be to set the mass frequency fail high to 1hz. find this table in the engine diag section within the airflow tab. Then unplug your maf sensor if you wish. Since these engines come with a separate IAT sensor in the throttle body hat. Remove your maf channels from the list. and your set to tune your VE table without skewing the data with the MAF. I couldn't say how lean or rich your going to find your VE table but you can use your VE AFR error graph to correct the table. don't forget to use the smooth function to keep the table from getting terrible dips and spikes. Im not sure exactly how you could put this computer into an OL Maf without a high rpm cutoff within the dynamic section of the airflow tab. I'll get flamed for this but putting your wideband sensor in your sensor 2 location after the cat isn't going to skew your WOT AFR readouts. but will skew your part throttle AFR. You can tune the truck in closed loop via fuel trims and still tune the WOT stuff without worrying about skewing your data. Iv'e noticed that when the flow volume across the cats is at its highest the cats are remarkably inefficient. I've personally tested this on my wifes 07 tahoe and seen less than .2 AFR variance between the sensor 1 location pre cat and sensor 2 location post cat.

[ChaseJ]

Thank you for the help. I will give this a shot when I get a chance this weekend.

Thank you again!

[ChaseJ]

Changing the MAF fail frequency and unplugging the MAF sensor worked. I was not able to make any changes in the VE table as I spent most of the day trying to get my wideband in HP Tuners to match the wideband in LogWorks. Finally got it figured out and then had to stop and do other things. Thank you for the pointers.

[5FDP]

I forget on the those older MAF's but if the IAT is built into the sensor you do not want to unplug it. The temp will revert to -38 and throw everything off.

[Oleblu]

On the vortec 350 engines they come stock with a seperate IAT. Mounted within the throttle body hat its a weird design very prone to IAT heatsoak. The maf is the old style 3 wire with only 12000hz resolution.