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General O2 won’t cycle Andy fuel trims are lean

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DsmDanielson

Proven Member
104
0
Jul 13, 2016
Peoria, Arizona
So I’ve been searching this forum all day and nothing is quite similar to my situation. Here’s the scoop;

1. My car starts and drives fine, I have stock injectors in right now, 12 psi of boost off a small 16g, Afpr, walbro 255 (not rewired)
2. The issue is I noticed my gas mileage is a bit worse than before. About 200 miles from full to empty. 18mpg, is not okay, and I mainly drive on the highway and I don’t have a lead foot.
3. Checking my logger, I noticed my o2 sensor doesn’t cycle at idle or cruise, only briefly after I decelerate and then get back on the gas.
4. My fuel trims are 24.2% for STFT and 15.8% LTFT when in Closed loop for that brief period, and 4.7% STFT and 0% LTFT in open loop. That means I’m running lean, why am I losing mpg then?
5. I unplugged my MAF and my idle just surged momentarily and then it went back to normal. I thought my car was supposed to die?
6. I unplugged my brand new o2 sensor and nothing happened at all. But I did get a heater circuit cel after a minute or so. I’m so lost.

Pointers: Can it be my ecu? My tps shows 0.8 and 98% on the logger respectively, I hear a clicking once in while from within my dash, my fuel pressure is set for 43.5 base pressure, and I don’t have any significant leaks, not to cause a lean condition like that.

If I’m running lean, why is my gas mileage plummeting anyway? I posted a log after driving home from by buddies house (freeway driving) and then AFTER letting the car idle for a few minutes, I screenshotted the results.
 

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Edit: I forgot that I resetted my ecu, and once I got a coolant temp of 180 degrees, my LTFT started leaning out to 12.5 but STFT stayed at 24.7 in that brief closed loop period. It shows 4.7 in my screenshot because the car is in open loop at idle ‍♂️
So I’ve been searching this forum all day and nothing is quite similar to my situation. Here’s the scoop;

1. My car starts and drives fine, I have stock injectors in right now, 12 psi of boost off a small 16g, Afpr, walbro 255 (not rewired)
2. The issue is I noticed my gas mileage is a bit worse than before. About 200 miles from full to empty. 18mpg, is not okay, and I mainly drive on the highway and I don’t have a lead foot.
3. Checking my logger, I noticed my o2 sensor doesn’t cycle at idle or cruise, only briefly after I decelerate and then get back on the gas.
4. My fuel trims are 24.2% for STFT and 15.8% LTFT when in Closed loop for that brief period, and 4.7% STFT and 0% LTFT in open loop. That means I’m running lean, why am I losing mpg then?
5. I unplugged my MAF and my idle just surged momentarily and then it went back to normal. I thought my car was supposed to die?
6. I unplugged my brand new o2 sensor and nothing happened at all. But I did get a heater circuit cel after a minute or so. I’m so lost.

Pointers: Can it be my ecu? My tps shows 0.8 and 98% on the logger respectively, I hear a clicking once in while from within my dash, my fuel pressure is set for 43.5 base pressure, and I don’t have any significant leaks, not to cause a lean condition like that.

If I’m running lean, why is my gas mileage plummeting anyway? I posted a log after driving home from by buddies house (freeway driving) and then AFTER letting the car idle for a few minutes, I screenshotted the results.
 
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