Tuning my '90 C4, L98 SD engine. Just put in an ACDelco AFS21 sensor. Not sure the old one was really bad, but certainly old. Had my BLMs fairly good, now they are all below 128, roughly 119-126. Not that bad, but on the rich side. Anyone seen this trend, after a new O2 sensor installed? I can certainly change my VE tables, ratio them down, of course. And, does a new sensor need some break-in time? like several hot-cold cycles?
TIA,

 

If you tuned around a faulty O2 sensor before, it would stand to reason that you'd probably need to retune around a properly working one.

 

That certainly makes sense.....not sure my old one was faulty, no codes and it switched ok......more like replacing it as a maintenance item.

 

Have had similar experience when replacing O2s. I guess that’s why u should change them w each plug change also.

 

02 sensors get lazy and drift over time. Not uncommon to replace them and gain 1-2 mpg on older vehicles.

 

Had my LT5 tuned pretty well going into the spring. In March I did a couple of maintenance things including new air cleaner, oil change, and some new plugs. Still running well, BUT I found that the motor was on the rich side. Perhaps some of my maintenance enhanced the efficiency, so I’ve ended up doing some more tweaking of the VE and SA tables going a bit leaner on VE and increasing SA a few degrees more. Now I’m back to being within +/- 3 BLM. A smooth DOHC sounds like a turbine winding out.
But I am considering installing new O2s. This tuning thing just never ends. Sometimes it feels like you’re Alice following the Rabbit down the hole.

 

I hear ya. Tuning seems never ending, but at least it is fun! Seems like changing the air cleaner would make it leaner, not rich. Not sure new plugs would make a difference. On a side note, I replaced the air filter in my favorite grass cutting lawn tractor, and now I can get more cutting miles on a tank of fuel! I'm sure tuning a LT5 is even more challenging.....would love to see one, let alone hear one!

 

Here you go. Those are Z06 NPP tips. Motor has intake and exhaust cams.

 

I loved my DOHC V8s. I have had 4 of them.

 

The LT5 is finally getting its recognition particularly with the intro of the C8Z06 LT6. Prior to the C8 Z, the LT5 was the only unique/bespoke motor ever built and installed for the Corvette.

 

exactly... lol. I have to force myself to leave my laptop at home when I drive the Camaro now so i can break the addiction!

 

I use an Asus tablet. AAARGH! Too easy to datalog.