Ive got a 5.3 LS that when cold and started, it surges, sometimes almost to a stall. It does this until it seems the engine warms up and then its fine. I get no codes and all vacumn lines appear intact. Any ideas where I need to start?

 

I would start by plugging a scanner in that can view real time data and see if on a cold start the coolant temp is the same as the ambient temp. Some times the cts will read only one temp and the car will run like crap till it reaches that temp and run fine. It has also happend where they will run great cold and not hot.

 

when the engine is cold it is running open loop... ie the ECM is using an algorithm / table look up control scheme to control air fuel ratio... once the oxygen sensors warm up and the water is above a certain temp it will transition into closed loop control where the fuel trims, etc are adjusted based on real feedback from those sensors

if you have quite a different set up from whatever ECM you got the original application from, ie air intake, cam, headers, etc, the open loop model is going to be off and requires some tuning to get the right Volumetric Efficiency table, etc adjusted... Idle tuning and control is the tough part, WOT is easy.

If you have made these types of changes and have a speed shop with reasonable tuning capabilities near by i would suggest you consider that, unless you have your own tuning capability

 

has it been tuned?
You can try cracking the throttle blades open slightly.

 

I had similar issues when I first got my car on the road last spring. As mentioned above, I had to play with the plates on the throttle body along with replacing the MAF sensor, IAT and TPS.
Also, where is your MAF sensor located. I originally had mine down line towards the cone which created turbulant air resulting in idle issues. Once I moved it closer to the throttle body things cleared up.

 

i am using all the stock components and ecm. i haven't used any aftermarket or deleted anything. the maf is closer to the airfilter location than the throttle body.
this throttle body is an electronic unit with no iat to remove or replace that i can see. i don't even see a way i can adjust the blades on it.
im going to check the cts first then work from there.

thanks guys. i appreciate it.