GMC van issues
 

I have an 06 GMC Savana with a 5.3L.
Runs like a top except intermittently it stalls out a few times while starting then for the first 15 min it stalls when decelerating or stopping.
It doesn't show any codes the only thing I see is the volts drop from 14 to 9 then it stalls or it revs back up.
Have taken it into GM and my mechanic but doesn't act up when I bring it in.
Has anyone had similar issues? or any insight as to what it could be?
Thanks

Take the throttle body off and clean it really good, make sure the idle ports are clean and check the outside of the throttle body and make sure there are no holes rubbed through it. I had a truck in doing a similar thing. I found a hole rubbed through the casting on the bottom side by the butterfly shaft. Changed the throttle body and problem solved. I'd also check sparkplugs.

Fuel filter

After the throttle body and plugs consider the MAF sensor and upstream O2 sensor.

I had a similar problem with my GM and after getting a new o2 sensor it's been great.

Another suggesting would be to search the internet for those with a similar problem. Most vehicles fail in the same way and someone else has surely already spent the time and money figuring it out.

Check wiring harnesses.

If it’s dropping to 9 volts while driving, the computer is losing voltage and the injectors won’t fire.

That’s where I’d start unless your cluster was wonky before this started

sounds like it could be idle control valve.