I have a 1998 Suburban K1500 5.7 vortec. Starts and runs like a dream for 5 or 6 seconds then slowly sputters out. If I touch the throttle during the 6 seconds it immediately konks out.

If I unplug the maf and map sensors it will keep running, nice and smooth, respond to throttle etc. (default maps are running it?) so I don't think it is fuel pump pressure related or security related. I already replaced the maf sensor, no difference.

Anyone?

 

You likely have a bad fuel pressure regulator IMO. I own a 1998' K-1500 so that would be my guess, even if you don't. Unplugging the MAP sensor won't change that, but you can change it out if you'd like to. Personally, I'd run a fuel pressure sensor on it. 55-to 62 PSI is considered normal with 60 PSI being ideal.

 

Welcome from Florida. Is the check engine light on?