My truck information is as follows:

2001 Chevy Silverado 2WD

5.3 liter V8

Mods: Powerbond underdrive balancer, Pacesetter Long Tubes, ORY pipe (deleting cats and down stream O2's) MSD wires, TR55 plugs, K&N Filter (stock air box), dynomax muffler, custom tune for Predator by RPMOnline.

Problem: 151 O2 circuit low voltage, 174 system too lean bank 2, and 300 random misfire. I instinctively changed the plugs, went back with TR55's. The passenger side was black, the drivers side was normal. After changing the plugs, it ran ok for a few miles, and went back to it's same tricks. Hesitating/missing when I give it the gas, rough idle, and it sounds like it's trying to stall out. The fuel mileage is horrible as well.

I've had these mods in place, complete with tune, for over a year with no issues or codes. I checked the wiring around the O2 sensor, and it seems to be intact. I sprayed carb cleaner around the intake gasket, and also around the vacum lines and air filter intake tube, no change. I pulled the vacum line that attaches to the fuel pressure regulator, and it was sucking like normal, and no fuel came out. (while running) It's progressively getting worse, and seems worse when the motor is hot.

I'm out of ideas and i'm not sure where to go from here. I keep the truck well maintained, and run 93 octane like i'm suppose to. Where do I go from here? What could it be, and how can I diagnose it? I've read through similar posts on the site, and though some of the information is similar, nothing matches entirely. This is my daily driver, and i'm worried i'll be with out a ride in the very near future. I am very reluctent to drive the truck if it is running lean. I noticed that in the end of the exhaust tail pipe, is very black. I did observe an exhaust leak on the passenger side, where the Y pipe connects to the header, in front of the O2 sensor. I can't imagine that is enough to cause these problems. Could a bad upstream O2 cause these issues?

Any help will be VERY much appreciated. Thanks in advance!

 

make sure MAF is clean, yes iw ould change both o2 sensors.

 

Your lean code on the passenger side could be because of the leak before the O2 sensor. The black plugs on the right side are an indication of over fueling. This would make sense if its getting un-metered air in the stream before the O2 Sensor. Over fueling could also cause the random misfire issue as well.

P0151 - O2 Sensor Circuit Low Voltage (Bank 2 Sensor 1)
P0174 - System To Lean Bank 2
P0300 - Random Cylinder Misfire.

FWIW
Bank 1 is DRIVERS SIDE
Bank 2 is PASSENGER SIDE
Sensor 1 is Before-Cat
Sensor 2 is After-Cat

I would recommend fixing the leak before the O2 sensor first and then try clearing the codes and see if helps. Most likely the 02 sensor is ruined and will need to be replaced. In order to properly diagnose a bad O2 sensor you need a scan tool that is capable of showing live data values so you can monitor if its functioning properly.

If that does not help you fix the lean issue, you may need to replace the Intake gaskets. The original Orange rubber seal's will flatten out over time and allow air to seep in. Even though the brake clean was done on the top you can't tell if its leaking on the bottom. GM changed the design on the later ones so they would resist ethanol and maintain it's elasticity better.

HTH!!!

 

Agreed, that exhaust leak will do exactly as 1FastBrick mentions. Get it fixed, replace the pass. O2 sensor and then see what issues persist.

 

i wrapped the exhaust leak, and replaced the O2 sensor. I drove it a little yesterday, and after the plugs caught up, the truck seems to be fine. I'll find out this afternoon for sure. I've been on my bike all day, but I have to take the trash to the dump. I'll post back up, and let you all know the result. Thanks for the thoughts too guys.

 

Did your O2 and exhuast leak help your issue??? you never posted anything if it did or not. I am having the same issue... I did watch my O2 go from 700+ to zero and stay there and it closed the loop.