Ok, my truck just doesn't have the power it should. I know it's just the baby 4.8 but it still isn't what it should be.
My personal opinion is that my Cats are clogged but I can't get the dealership to change them because it isn't throwing the right code. The only codes are for the rear O2's (to my knowledge)
So I took out my O2s and the front ones look fine but the back ones are pretty black. Also, I took out the plugs and they don't look all that bad.
I don't know what I need to do, I'm throwin all my money in the Tank of this thing averaging 13.5mpg.

My brother-in-law said something about the thermostat being stuck in open or closed loop might cause it to run rich???
I guess the computer would think the engine is still cold and causing it to use more fuel?

I don't have a clue so hopefully someone on here can help me out since I can't get anything out of the damn stealership.

 

well the rear O2's can measure the Cat efficiency, and they can also tell if you're having a lean/rich condition, what was the code that's being thrown? that would help understand where the problem is coming from.

As far as the thermostat, if its stuck open you would be able to see something awkward in the water temp gauge.

Are you running anythiing weird like oil with zinc in it? or did you ever try running leaded race gas? is the motor stock?

Also did you open up the CAI by any chance and not put the MAF back the same direction as it was before? that could mess up the reading

 

The only thing the Dealership told me was that the Rear O2s were throwing the codes but I didn't get the actual code number.

She's all stock , the MAF is right and I haven't run anything besides regular pump gas.

 

Not saying all dearlerships are shady but, i have yet to find one to trust with my vehicle. Take it to oriellys or auto zone and get the codes read. its free. Just get the codes, dont buy everything they try to sell you. Dont trust many of those guys either lol!

 

My buddy had a 08 RCSB 2wd, 4.8 60e 3.23s. Some reason it was horrible on gas. Think he was only gettin about 16 on the interstate if i remember right.
Traded it for a 2010 5.3 6sp. Dunno what he is gettin with it.

 

Damn, well, anyone else with some suggestions?
I'll try to get the codes today.

 

I know my 02 ran bad for a while, ended up being my knock sensors, but take it to a muffler shop and they should be able to check your cats.

 

Kind of hard to help without the codes. I would be surprised if the cats are clogged. For an 2008, seems kinda soon. They have to replace the cats if they are clogged at no charge due to national regulation, which states they have to last a minimum of 10 years.

 

Put a temp gun on the cats and record the temp. If they are over 400* at idle, then something is wrong. The rear O2's are the catalyst monitors. Dealership's are a JOKE and the Lil' kids working at them are even worse.

 

I don't even need a temp gun, I guarantee they are over 400*
They are way hotter than normal and you can feel the heat coming from them just standing next to the truck.
Today I busted out my cats, she runs a tad bit better but there's stilll something not quite right.

Any other suggestions?