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Can anybody just give me some quick insight into this issue with my car. 2014 Malibu LT, 2.5L. When at cruising speeds the car shows very abnormal values for fuel trims and o2 voltages. This also only happens when trying to set the cruise control. It seems to normalize sometimes, only when car is very warm and has been driven a long while prior. This car has an issue too, where after 2nd gear, every upshift comes with a complete lack of power after it. If you release off the accelerator after the shift, then slowly press down, the acceleration comes back, but after the upshift and car just bogs to nothing. I have no exhaust restrictions. I have no vacuum leaks. Fuel pressure on low side ranges from 40-60psi, on high pressure side its good too, pressures upwards of 1500-2000psi when accelerating. I compared scanner snapshots from an old ScannerDanner thread from a while ago to my car's scanner data, and nothing seems out of the ordinary. When at idle the fuel trims and o2 voltages act as they should. Upstream switches back and forth, downstream remains at about 0.7V.
At cruising speed (about 50mph):
stft = +30%
ltft = +40%
upstream O2 = 0.025V
downstream O2 = 0.035V (yes these voltages are typed correctly, they stay this low, and stay stuck there. Sometimes they go into normal operation, but sometimes this happens)
This car has a P0101 that will never go away. Smoke test shows no leak on intake and plumbing. MAF sensor replaced. Both PCV valves replaced. New GM air filter.
It runs pretty rough until very very warm, and has the loss of power after shift as stated above. Resetting foot and pushing down resumes decent acceleration.
So what gives!? The very odd fuel trims and O2 behavior and P0101 that never goes away makes me very confused. So I'm wondering if it's a computer issue I used to have P0300 and P219A, but those have been gone for a while now.
At first glance, it looks like either an actual problem with the fuel system or an air measurement issue.
Knowing if the engine load PID hits 100% (or more for a turbo) is a pretty good indication of the ability to accurately measure air coming in the engine, and match it with the correct fuel volume.
They are particularly sensitive to maf location and non laminar air flow. If there are any modifications to the air cleaner tube (cold air intake, K&N filter, removing of any screen or filter looking plastic bits some people may misidentify as an "obstruction"), return it to the stock configuration before chasing a fuel trim problem.
If it's a Flex Fuel car, make sure the fuel composition PID is correct. If it isn't, make sure it doesn't have E85 in the tank.
Ok, how about this multimeter voltage on all 4 pins of my upstream O2 sensor. This is the original GM O2 sensor, never replaced.
heater power - 12.5V (black wire on O2 sensor pigtail side)
heater (ground?) - 2.5V (black wire on O2 sensor side)
sensor (ground?) - 1.05V (white wire on O2 sensor side)
sensor (signal?) - 1.78V (blue wire on O2 sensor side)
Does this indicate some sort of issue with my 5V reference to the O2 sensor? Do O2 sensors even operate on the 5V reference, or is it somehow stepped down before the sensor? I checked the voltages the MAF connector to compare, and all values at that connector seem good, a perfect 5V reference on multiple pins, nothing seems wrong there.
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