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?

[Fummins]

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. Attachment 25077Attachment 25077

I had a Mirage or two throw that P0172 code and found the purge solenoid on the side of the cylinder head stuck open. IIRC another car had the vent hose was disconnected at the rear of the valve cover(found after dealer installed a warranty cvt).

[7milesout]

Bambam - BTW, the intake you have on that car, does look badass. My whole "bad cat" is just speculation. I may be out in left-field with that, all by myself.

I had an 83 RX-7 one hundred years ago. It ran pretty good. But one day, I drove leisurely through the neighborhood (no problems), then got out on the main road. I went to accelerate and it fell flat on its nose and wouldn't go but about 25 mph. A girl came along and got slam up on my bumper, and then started waving her hand in front of her face (implying it stunk).

Course that car was before OBD info. But it was apparent the cat went bad and was plugging the exhaust, and making rotten egg smells. Came on sudden like. But if I remember right, I had parked the car for a couple few weeks (as I had just bought another), and this was the first time I'd fired it up after that couple few weeks. I don't know catalysts very well. Maybe yours is fine, dunno. Maybe yours is slowly going bad. Maybe I should quit smoking crack.

[Bambam234]

You’re not gonna hurt my feelings any at all. The reason I was wanting a little more power is so that when the alternator comes on with the ac or hell even by itself it feels like I just stood on the brakes. I like the fact I get really good gas mileage I was just hoping it wouldn’t struggle so much for an alternator. I see the codes as conflicting one say rich the other says lean really the only reason I brought it up. I bought this car in pretty bad shape so all I am doing is polishing a turd I just like having fun with in the mean time. I really should have completely read everything I just realized you explained what you thought on the codes. It makes sense the way you explain it. The car has around 109k miles so bad cats is possible especially with how I found the rest of the car. Thank you

[Bambam234]

I think this catch can is simply causing more problems than it’s supposed to prevent. Your comment about the valve cover vent tube is similar to what I found earlier. I will remove it and see if it makes the difference

[7milesout]

Bambam - I never feel anything regarding the OEM alternator. But the A/C yes, does take a measurable toll. If your replacement alternator is taking a lot of power to turn, can you find an OEM or OEM rated alternator?

[Bambam234]

Yeah I have a 240 amp alt. My stereo is kind of big and I am charging 2 60ah lithium batteries. I know I am inducing my own headache with the bigger alternator on such a tiny engine I honestly thought it could manage the extra load. But that’s what has me hoping to get just a little more power from the engine.