So first time posting here. I have a 02 silverado 2500hd 6.0 278k
The issues I’m having are
1-it starts fine and after warming up it starts to have rough idle and hesitation from a dead stop.
2-There is a lag/hesitation from a dead stop like its in 2nd gear and not 1st (this problem doesn’t seem to be related to the above as its always done this)
3-Truck seems to be on the weak side…just does not have alot of get up and go.

Here are a few things I’ve done to it so far
new plugs
fuel filter
air filter
trans rebuilt (maybe 6000 miles on it)
new neutral ss
no cats ( this is strange cause there is no check engine light of any kind)
checked fuel pressure (at idle I’m getting around 42-45psi)
Any ideas on these would be great! Thanks.

 

Your fuel pressure is too low. Factory spec is 55 - 62 psi. You likely need a new fuel pump.

A dying fuel pump can cause the problems you describe.

Good Luck!

 

Sorry for the late update! So I installed a new fuel pump and the truck runs much better. It still seems a little weak but it is stock.

 

Good to hear. Now, remove the vacuum line from the fuel pressure regulator (it should be on the drivers' side of the engine just below the black plastic Vortec cap), and see if fuel runs out of either the vacuum line or the nipple on the fuel pressure regulator. If no fuel, the regulator should be OK. If fuel runs out, replace it because the internal diaphragm has ruptured.

Also, if you do not know how old the Oxygen sensors are, consider replacing them because they do get weak with age and mileage and then have an adverse effect on gas mileage. If you replace them, please only use Denso or ACDelco/GM GenuineO2 sensors in order to minimize future trouble down the road. Other brands can cause headaches. rockauto.com has good prices on O2 sensors.

Good Luck!

 

Thanks for the info.
I did the procedure on the fuel regulator and it checks out. I’m not sure how old the o2 sensors are. What is strange is I have no cats and there are no codes. The truck just seems to lack power. I’ve changed fuel filter as well.
It has a strange trans issue as well that I can’t figure out and I’m pulling my hair on that lol

 

I do not think there is a specific OBDII code for no catalytic converters being present. Closest would be an OBDII code for the upper and downstream O2 sensors having the same outputs.

Good Luck!