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Cold, Chugging GMC

The truck is a 4WD with the 4.8L V8, has 134k problem free miles. While pulling a camper trailer the Service Engine Soon light came on and was blinking. After removing the camper the light went away. Now the light has returned and blinks occasionally. The light is not the larger issue tho. When the engine is cold it is difficult to start and I have to hold the accelerator to the floorboard to keep it running or rather chugging but only on days when ambient temps are below 50ish. As the motor warms it chugs less and eventually smooths out. Once the engine has warmed up it runs as if there is no kind of problem. The service engine light stays on but does not blink. This all began suddenly tho there might have been a problem before but we recently moved to the Chicago area from the Phoenix area. A stop at the local auto parts store for a code read said the fuel pressure sensor is bad tho it seems there is something more than that going on. With a Chicago winter coming this needs repaired!

Why would you suspect something more going on?
Lack of sufficient fuel pressure, which could be caused by a failing fuel pressure regulator, could easily account for all your symptoms.

As a matter of fact, since the light went away when the load was removed, and a loaded truck or a cold engine needs more fuel than an empty one or a warm one, that’d be an excellent suspect.

Go. Get your fuel pressure and regulator checked. Post back with the results.

And, by the way, get the servicing up to date.
What year wasthis baby again?

same mt bike is correct, the fuel pressure sensor could cause this symptom, and should be disproved as a cause before considering anything else.

What model and year is this GMC? Could you provide the exact DTC code pulled? Is this truck flexfuel capable?

This truck likely has a returnless fuel feed system. It has a fuel pump control module that uses information from the fuel line pressure sensor to adjust power to the fuel pump. So if the fuel line pressure sensor is defective that could affect driveability.