Hey guys, been quite a while since I was on here, as the car was off the road for quite a while due to an unfortunate incident with a Kia driver on his phone. I've been fighting issues since I got the car back together last summer. This is the latest:
I have an AEM wideband gauge in my car and it's been running super lean. I'm not totally sure when this started, as it had a bad miss when I put it away for the winter (just a bad plug wire). Prior to that it was running pretty well. Ever since I took it back out, it's idled around 16:1 on the gauge and shoots up around 20 (or just says "lean" if it goes too far) if I get into it at all. Looking at the fuel trims, the B1 BLM is pretty consistently around 150 and B2 seems to be good around the ideal 128. Definitely seems to be lacking power, although I don't want to get on it too hard, given how lean it is.

I don't really think the Opti would cause this anyway, but since that's the go-to scape goat, I have a new Petris industries Opti. (Old Cardone Opti died on me last fall).

I know there's quite a few things that could cause a lean condition, so here's what I've tried:
Replaced the regulator without checking pressure, as I initially thought it was a fuel pressure issue (stupid and lazy, I know).
Bought a gauge and checked fuel pressure, seems pretty happy at 42 psi with the vacuum line off the regulator.
One O2 looked a little weird on the graph intermittently (would fluctuate like it's supposed to and then go flat for a while, then back to normal), so I replaced the O2s. That fixed the O2 readings, but did not fix the lean condition. See the attached photo of the O2s that came out, passenger side is white.
Found and fixed a couple small exhaust leaks, no change.
Sprayed carb cleaner around at locations of possible vacuum leaks and listened for RPM changes, found nothing.
Cleaned all 8 injectors (carb clean with a battery connected to fire them), spray pattern looked consistent across all of them.

So to sum it up, we're adding fuel on the driver's side (B1), not doing anything on the passenger side (B2) but appear lean on a wideband, and appear to be running lean on the passenger side, based on my white O2 sensor...

Really out of ideas for what to try here... I have a scan from EEHack, that I can't seem to attach. I do have a scan from Scan9495 attached, but it's just closed loop idle, probably not super useful unless something immediately jumps out to you guys. I'll take a better one and add it. Hoping maybe someone can see something I can't.

Might also be worth noting, EGR is removed (both physically and from the tune) because it fit really poorly in the headers.

 

Took a look at the O2 sensors in closed loop. The Bank 1 numbers seem normal, with a range of 0.004 - 0.892 volts (a little low on the rich side) with an average of 0.428. That would seem to confirm the system is adding 19.5% extra fuel on the left side to keep it from leaning out. But there's something weird with the B2 numbers: range 0.018 - 0.835 volts (again a bit low on the rich side), but the average is only 0.271 volts. Ideally, you wan the average to be 0.450 volts, indicating the sensor is cycling back and forth from rich to lean correctly. But why is Bank 2 showing such a low average? Would seem to indicate a lean condition, that isn't being corrected with the 2.3% addition on the 131 LTFT.

Color coding the high vs low readings on bank 2 seems like there are periods when it just hangs deep in the lean zone (slow response), then hangs in the rich zone (slow response).... but not high in the rich zone.

Where is the wide band located?

What brand are the replacement O2 sensors?

Try swapping the O2 sensors side to side. If the keeps everything the same, try swapping the injectors side to side.

 

Always good to have your input, Fred. You've been helping me (and countless others) since day one with this car.

They're Bosch O2s. I've never had an issue with them on other cars, but seems like they maybe have some mixed reviews here? The lean issue does pre-date the sensor swap. I can probably do a swap side to side this weekend. I could even swap the originals back in and from side to side (didn't get rid of them, and it's pretty easy to tell which was where). The wideband is about 8" back from where the two banks Y together. I considered swapping the injectors, kind of kicking myself for not doing it while it was apart, but, oh well. Pretty quick job, anyhow. Is the low average more likely indicative of a bad sensor or of a bad mixture that the sensor is picking up?

 

Good question. For some reason the PCM doesn’t seem to be reacting to the lean condition. I need to go back to the log and look at the short term corrections. When the sensor voltage indicates less than 450mV for an extended period of time, causing the STFT's to stay above 128 for an extended period of time, the PCM should ratchet up the LTFT's. I was too focused on the low average readings on the passenger side. But thinking about it more, I need to go back and check the short terms, Wait to make any swaps. My brain is still recovering from preparing my income tax over the weekend.

Also wonder if the PCM bias voltage to the sensor is not at the correct 0.450 volts. Would have to test that with the O2 sensor unplugged. Has to be done with a high impedance multimeter, to avoid damaging the PCM.

 

Did you have any more thoughts or have a chance to take another look at logs? I have a multimeter, I could check voltage to the o2s and give wiring another once over if you think that’s a possible issue. I’ve been wracking my brain, still can’t think of anything else as a possible cause. I could go drive the car while logging if there’s a particular scenario you’d want to see data for, too

 

FOUND THE SOLUTION!

As is so often the case, incredibly simple fix to a seemingly complicated problem. It's actually 2 issues: the intake elbow was rubbed through on the bottom creating a huge vacuum leak - that was causing the rough running, low power, erratic behavior. I searched high and low for vacuum leaks and somehow managed to never give that a close look. Inexperience will do that. Fixed that by replacing with a TFS aluminum unit. After that, car ran great again (still the occasional pop from the exhaust at light throttle in first, but it always kinda did that), but the AFR gauge was still generally reading lean. Very erratic readings, though, which made me suspicious, considering how good the car felt. After hooking my laptop back up and cruising around, the O2s that the PCM reads seem to be happy. Given the data from the O2s in the headers and the general good seat of the pants feeling, I'm gonna say the car is fixed and the gauge has an issue. I'm thinking maybe the wideband got fouled when the car was running poorly. The gauge can wait though, for now I'm just going to enjoy having my car back in between rainstorms.

 

Thanks for the follow up.