Erratic idle and now check engine light

[7milesout]

Quick update car has been running great but have been getting a check engine light for P0172 (system to rich (bank1) just haven’t had enough time to troubleshoot it. I will post a screenshot from the Carly app that I used to scan it because it’s odd in the permanent issues it shows p2096(post catalyst fuel trim system too lean). I did find a hose barb that I believe will work just want to make sure it’s secured well. Has anyone found a reliable way to get a little bit more power from these engines? Without going nutz and doing a stand-alone ecu to get better tuning ? Poor little engine doesn’t like the new alternator and I don’t think a second alternator is feasible with this engine.

Bambam - this may sound mean, unsensitive or like I'm snipping at you. But I'm not. WHY would you want a little more power? Even with 20 more hp (which is way more than any of us are going to get without forced induction), it's still going to be whomped by a Honda Fit and/or a poorly running Honda Civic. My point is, just get it running in nominally and sit back and enjoy the advantages the 3-Tapper (not enough power to bang) provides you. Fuel savings and more money in your pocket. That is the point of the car. More power will get you nearly nothing.

As to your codes, things are complex. I'm battling or have been battling codes in my GMC Sierra. I tend to take codes too literally. As to your combination of codes, I'm just going to offer up speculation. Post catalyst, as I understand, the O2 sensor should always read rich. Why? Because the catalyst reaction, no oxygen is supposed to come out. Just carbon dioxide, Nitrogen and water. Since a post-cat oxygen sensor NORMALLY sees no oxygen, the resultant signal is deemed to be rich. Which to the ECU that means it is running correctly and no fault codes are generated. In an actual rich burning condition, all the oxygen is consumed with extra gas (or diesel) left over. That's why the post-cat O2 sensor should read rich (should be no O2 if the catalyst is working correctly).

My assumption is your catalyst is going bad, and even choking up your system a bit. Why? It saying lean post-cat is a reason to think it is going bad, it's not properly doing its job. Choking off your system a bit, causing your cylinders NOT to get the full amount of air that the ECU is programmed to fuel for. The result? 1. Lean post cat (failed cat). 2. System too rich because it's not getting enough air. And 3) you mentioning about getting more power. I'm betting you're down on power (and maybe down on mpg a bit too) and that's the reason you're asking the question about how to get more power.

My guess is your cat has been slowly getting worse. Slowly enough you haven't directly noticed it lacking power. Similar to the situation with the pot of water and the frog. Do you check / measure / record your mpg?