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I have a LM7 out of a 2002 silverado that's swapped into an F-Body. It's got a mild summit cam, a jegs fabricaterd intake with stock truck injectors, a 102mm throttle body, and ebay long tube headers. It's been running fine up until recently where it has began falling on it's face under load. It stumbles and backfires under load. so I got to diagnosing. So far I've replaced the o2 sensors with denso replacements, replaced all plugs and wires, briefly checked the o2 sensor wiring, checked the injectors, swapped coils around and verified spark, and checked for vacuum leaks, and pulled the valve covers to verify no broken springs or collapsed lifters. Today I hooked HPTuners up to it and scanned it with the VCM Scanner and found that the o2 readings were inconsistent with each other. Now my understanding with how narrow band o2 sensors work is that they should fluctuate between 100 and 900 mv constantly which is what the passenger side bank is doing. The driver side on the other hand (bank 1) is sticking around 100-200mv. This is causing the fuel trim for the driver side to shove all the fuel into that side of the motor. Now my question is what would be causing this to happen? I would think that a bad o2 sensor would be causing the readings to stick at 450mv and not move, and paired with the fact that I just replaced them I don't think they are the issue. I'll have the logs attached. Any help appreciated. thank you.
You have to remember that an O2 sensor doesn't measure "mixture". It measures OXYGEN. More specfically, it measures the OXYGEN in the ATMOSPHERE, compared to the OXYGEN in the exhaust pipe; which is why its output (it generates a voltage) goes high when there's no OXYGEN in the exhaust (which would ordinarily be interpreted as a "rich" condition in an otherwise properly running engine). So, THIMK: if you have a cylinder that's not firing (aka "missing"), it's dumping a full load of OXYGEN into the exhaust every engine cycle, which the ECM sees as "lean", therefore the ECM adds fuel.
No a defective O2 sensor will not "stick at 450mv and not move". More usually it won't generate any voltage at all, although sometimes they just get real lazy and don't generate the proper voltage, or they're very slow to respond.
Fix your ignition problem first. The O2 sensor readings are gonna be WACK until you get that taken care of.
You have to remember that an O2 sensor doesn't measure "mixture". It measures OXYGEN. More specfically, it measures the OXYGEN in the ATMOSPHERE, compared to the OXYGEN in the exhaust pipe; which is why its output (it generates a voltage) goes high when there's no OXYGEN in the exhaust (which would ordinarily be interpreted as a "rich" condition in an otherwise properly running engine). So, THIMK: if you have a cylinder that's not firing (aka "missing"), it's dumping a full load of OXYGEN into the exhaust every engine cycle, which the ECM sees as "lean", therefore the ECM adds fuel.
No a defective O2 sensor will not "stick at 450mv and not move". More usually it won't generate any voltage at all, although sometimes they just get real lazy and don't generate the proper voltage, or they're very slow to respond.
Fix your ignition problem first. The O2 sensor readings are gonna be WACK until you get that taken care of.
I'm under the impression that it's not dumping oxygen into the engine, but fuel into the engine causing it to run extremely rich and thus causing a misfire on that side. It's my understanding based off of the graph from the scanner that what's happening is since the sensor is reading lean and never going above 450mv it's telling the engine to add mre and more fuel until the fuel trim is maxed out causing a very rich condition. If I'm wrong please correct me but that's my understanding of the situation.
You're partially right, but not paying attention to the part you're wrong about.
The O2 sensor doesn't measure "mixture". It doesn't measure "lean" or "rich". It doesn't do ANYTHING EXCEPT respond to OXYGEN. When the difference between the level of oxygen in the atmosphere and the level of oxygen in the exhaust is zero, the sensor's output is zero. When those levels are different, i.e. when ALL of the oxygen that the engine has ingested has been combined with fuel, then the sensor's output is high; a little 1V.
What your O2 sensor is telling you, by its output always being near zero, is that there's LOTS OF OXYGEN in your exhaust. The only way this can be happening is, one or more cylinders are misfiring.
When a cylinder fails to fire, an entire charge of FUEL (which the O2 sensor is COMPLETELY oblivious to) and OXYGEN - which the O2 sensor DOES respond to - gets dumped into the exhaust. A misfire thus causes the O2 sensor to report what is in effect a "lean" condition (excess OXYGEN) to the ECM, thereby causing it to add more fuel in the attempt to bring the OXYGEN level DOWN.
The reason the O2 sensor's output never comes off of zero is because THERE'S A MISFIRE. Therefore there's EXCESS OXYGEN in the exhaust stream. Therefore the ECM goes nutz trying to put in more fuel.
Fix the misfire that's causing the O2 sensor to be dosed with excess uncombined oxygen before trying to deal with the fuel trim issue.
You're partially right, but not paying attention to the part you're wrong about.
The O2 sensor doesn't measure "mixture". It doesn't measure "lean" or "rich". It doesn't do ANYTHING EXCEPT respond to OXYGEN. When the difference between the level of oxygen in the atmosphere and the level of oxygen in the exhaust is zero, the sensor's output is zero. When those levels are different, i.e. when ALL of the oxygen that the engine has ingested has been combined with fuel, then the sensor's output is high; a little 1V.
What your O2 sensor is telling you, by its output always being near zero, is that there's LOTS OF OXYGEN in your exhaust. The only way this can be happening is, one or more cylinders are misfiring.
When a cylinder fails to fire, an entire charge of FUEL (which the O2 sensor is COMPLETELY oblivious to) and OXYGEN - which the O2 sensor DOES respond to - gets dumped into the exhaust. A misfire thus causes the O2 sensor to report what is in effect a "lean" condition (excess OXYGEN) to the ECM, thereby causing it to add more fuel in the attempt to bring the OXYGEN level DOWN.
The reason the O2 sensor's output never comes off of zero is because THERE'S A MISFIRE. Therefore there's EXCESS OXYGEN in the exhaust stream. Therefore the ECM goes nutz trying to put in more fuel.
Fix the misfire that's causing the O2 sensor to be dosed with excess uncombined oxygen before trying to deal with the fuel trim issue.
So based on what you're saying should the misfire I'm having should be caused by a lack of fuel going to one or more cylinders in that side of the engine and causing the o2 sensor to report ton of oxygen? I think I'm beginning to understand what you're saying but I'm still a little confused.
You're dealing with a chain of events here that leads in a logical sequence. Here's the chain:
Misfire = OXYGEN gets delivered into the exhaust in the form of unburned air/fuel from some cyl that's not running... that means, RAW FUEL which the O2 sensor can't see, and lots of OXYGEN since it just passed through the engine unchanged
–>
OXYGEN in the exhaust makes the O2 sensor report the presence of OXYGEN to the ECM (remembering of course, that the OXYGEN sensor sees only ONE thing in all the world - OXYGEN - in its own very single-minded way)
–>
OXYGEN in the exhaust tells the OXYGEN sensor that there's OXYGEN in the exhaust (duh), precisely because that particular OXYGEN didn't burn any fuel
–>
ECM gets message "oh there's LOTS of OXYGEN in there, I guess that means there's not enough fuel" because that's all it's ever been told how to interpret this signal
–>
ECM dumps in more fuel
–>
You datalog the ECM
–>
ECM tells you "All I can see, is too much OXYGEN in the exhaust (less than half of full scale coming in from the O2 sensor)" at the same time as it says "I'm bumping all the fuel trims up as high as I dare, to try to put enough fuel in there to combine with all this OXYGEN that the OXYGEN sensor is telling me is in there"
–>
How is ANY of this this confusing?
Fix the misfire before you try to work on the fuel trim problem.
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LM7 misfire and O2 reading low 
