i will say when the 0-2 sensor went bad i had to turn off closed loop so as not to foul my spark plugs lets see you do that with a needle and seat stuck and i sat in the car with the cold a/c blowing and tap 2-3 i-cons and wala down the road runner i go
I had an 02 go south on me. Luckily the tune had been steady for long enough to where I turned off the learning function. The learn table cells were all in the single digits and most were under 5. At that point it basically acts like a carb since there is no feedback from the 02 trying to match the set A/F values.
Turning off learning actually saved me from internal engine damage. There were some bad exhaust leaks that I didn't deal with right away and kept driving it. With no 02, the ECU would have been dumping extra fuel to compensate for the extra air. Too much unburned fuel creates excess carbon buildup, fouls plugs, washes the cylinders down with gas and dilutes oil lubricity = bad! But, after locking down the tune the ECU will not learn based on any new A/F conditions. (like a carb!) Luckily the tune was slightly on the lean side when it was locked in so it didn't overcompensate for the extra air by dumping extra fuel. Eventually the exhaust leaks got bad enough where I had to fix them but I dodged a bullet for sure.
In general I am skeptical of blaming the 02 (same with the ECU). I see it get named as the cause of any number of maladies but no one ever checks them to see if they are actually switching. I bench tested mine and sure enough it had stopped switching so time to replace.
Note how black the throttle body bores were. Thankfully that buildup was really the only issue - still had good oil pressure and it didn't smell like gas.
To be clear, I've spent some time in my life fooling with many differrent types of carburetors. I've gotten some decent results from my efforts like getting good mileage out of a poorly mismatched engine combination. I can fix bogs, surges, rich and lean conditions, etc. It's fun but due to their mechanical nature, you are limited in how precise you can get the tune and there's always going to be something that's not quite right depending on how you drive. WOT is simple but trying to get a carb perfect for all normal road driving conditions can be challengeing.
EFI allows the user to get much closer to 'prefection' because there is finite control over all parameters of the tuning process. That's also why it makes zero sense to not let the ECU control the timing - EFI is about precisely controlling all tuning parameters, not just the fuel. This is especially true when you build your own tune and go through the adjustment process as it learns. It's rewarding when you get a combination to run as well as it can under a variety of conditions. It's proved out by data logs and the information in the learn tables. If you get to a point where the system is no longer learning, you've done well.
If you don't care about that or don't have the desire to get involved with the tuning process, stick with a carb and accept that it's always going to be a compromise on some level. It's the same with letting the ECU do it's thing without any input from the user. As they say, garbage in, garbage out.
