2004 burb spits, sputters, almost stalls, then surges (revs up)
 

Hi, I am experiencing a new issue with my burb, it is a 2004 z71 when driving typically at low speeds or idle it will run rough as if it is going to stall, but never does then it will correct itself often by reving up (hold on). This has gotten to be quite dangerous if following traffic sometimes having me throw it into neutral. Just recently it actually did it on the highway as well, and appears to do it more frequently when warmer and wet out. When it is cold it seems to work fine, and it only does it when the truck/engine is at operating temperature. Also there is no messages or codes or lights on.

To date I have taken it to the dealer numerous times, with no luck. Engine/wires sprayed with salt water -no issues, runs perfect
Plugs are new with updated # and gap as per tsb
MAF and throttle body cleaned
Cats checked and O2 sensors
Again no codes whatsoever

What I have also noticed is when it is happening if I try to accelerate it makes it worse, as if it will stall, so I just completely step off pedal let it catch itself then try again.

In some cases rpm has fallen below 200 then will surge to like 1000+ then return to normal 600.

Any help appreciated, as it is making it very unreliable and unsafe.

Thanks in advance.

Did they check the fuel pressure?

Yes it was checked in December before Christmas, and all was good. But of course the truck would not act up when being tested.

Today with it being cold outside truck ran perfect, does this make sense that it would potentially be the fuel pump and/ or fuel regulator? It only seems to do it when above 0 C and it is intermittent, please help.