2004 Chevy Silverado 2500 with the 6.0 running rough

[AuroraGirl]

Hi there,
Still having problems.. I pulled the map sensor out and it was dirty with oil, so I cleaned it very well and put it back in. It did seem to run a little better but still didn’t fix the problem. It’s reading 12 inHg on my scan tool. I checked the fuel pressure and it’s at a constant 55-60 with key on and at idle. I took a look at my fuel trims on it aswell and there is one odd ball. Both of my stft are at 0 but ltft 1 is at -3.9, but the ltft b2 is at 25% and seems to stay there. From what I’ve researched the 25% is not an ideal number to be having. Not sure if that is a o2 senor problem and what one it would be to cause only one bank to have a high fuel %. Any ideas? Thanks

Whats your elevation? Ambient pressure at your elevation might be 12 inches of mercury
Where im from thats almost 2 inches of mercury low, but im only about 1000 ish feet above sea level, if that.


25% means your fueling control has maxed out its ability to compensate, and 0% means its probably not applying any immediate corrections with oxygen sensor readings

Id look at your mAF sensor, clean it with maf spray on the elements, ensure your intake tube has 0 leaks after your MAF sensor, then inspect for exhaust leaks. Gross leaks will do this, but the "cracked manifolds" these trucks have shouldnt be that extreme. The O2 are right after the pipes im pretty sure, so you shouldnt have much leak potential before that.

Id suggest using a propane torch, unlit , with your intake all buttoned up after cleaning the maf. put propane on top of the intake manifold along both sides, by where the boot connects ot the throttle body, and then up toward the MAF sensor but never on the left side of the intake box (Thats where it pulls in air)
If you dont get any idle climbing , your fine there.

If your elevation doesnt make sense for 12inches mercury, then id say you have issue there

Im assumign the reading you were reporting was BARO
(barometric)
MAP while idling should be like, 9x something KPA (Idk what that is in sae, my scan tools report pressures in metric so I go by that)
MAP while holding throttle should be less
you should also use a vacuum gauge on the engine, see what you get at idle

 

[AuroraGirl]

To follow up on that, I did notice a exhaust leak about 2 feet behind the o2 sensor but it is on the x pipe so both banks should be effected but it appears that only bank 2 is having problems. I might just have to send it to the shop. It’s driving me nuts

bank 2 sensor wont be at play here.

Where is your o2 sensors relative to this "x pipe"

Im thinking of mine, where the manifolds go into the y pipe , they each have an O2 right there by each manifold. is yours like that
Like this

 

[Chevy2005]

So I have longtube headers and yes on those headers there is a o2 sensor, then it goes to a x pipe and has true duals going all the way back. The more I look at it the more I think it may be that exhaust leak. Because the driver side o2 sensor is much further away from the exhaust leak than the passenger. That would explain why I have bad ltft on bank 2 because there is not much back pressure. The x pipe has a crack all the way around and It definitely leaks pretty bad. So I’ll probably start by fixing that.

 

[AuroraGirl]

So I have longtube headers and yes on those headers there is a o2 sensor, then it goes to a x pipe and has true duals going all the way back. The more I look at it the more I think it may be that exhaust leak. Because the driver side o2 sensor is much further away from the exhaust leak than the passenger. That would explain why I have bad ltft on bank 2 because there is not much back pressure. The x pipe has a crack all the way around and It definitely leaks pretty bad. So I’ll probably start by fixing that.

i forget the distance but at least 6-10 inches past the o2 needs to be sealed to not affect it