I have a 2003 Silverado with 5.3. The check engine light came on and the code was for O2 Sensor. Before I shell out the money on new o2 sensors I would like to know if these symptoms are in fact caused by faulty sensor. When i start truck when its warm, sometimes the RPM's will fluctuate a little and also sometimes run very rough then it will start idling fine. I have noticed sometimes at wide open throttle it will be very sluggish. Yesterday I took a 150 mile trip and it ran ok the first half but on the way back it was running rough, It would run fine at idle and very light throttle but anytime i would put truck under load it was like there was no power, it would lose speed but if i worked the pedal i could get up to highway speeds and would run fine until i needed to pass someone. Do those symptoms sound like bad O2 sensor or what? The truck seems to run rougher when engine is warm. At a loss here.

 

Yeah sounds combination of your o2 sensors and that light. That check engine light sounds like it is putting your truck into limp mode and that is your cause for the no power also, when your o2 sensor goes bad it is throwing your fuel/air mixture because it is getting a faulty reading. More than likely because of a default, it is probably dumping all kinds of fuel into the motor because it doesn't know what else to do. Also, if you decide to do o2 sensors, look at a vid on youtube, o2 sensors are actually really easy to change with a ratchet and o2 sensor socket from any autoparts store. Hope this helps you out.

 

Well the new o2 sensors didn't resolve the problems. I have noticed that it runs better when engine is cold and as it gets warmer it runs worse. Any clues?

 

Coolant sensor might not be operating correctly.

 

Have you done a fuel pressure check yet. Sounds like you might be having a problem with the injectors...

 

Or it might be a faulty fuel pressure regulator