Fuel pump or pressure regulator on its way out?

Mossyoakglock · July 23, 2014

2008 Silverado CC 5.3L.

This has happened twice in about two weeks.

Truck sits overnight for about 13-14 hours until I get up and go to work the next morning. I start the truck and it cranks fine and turns over quickly but has a rough idle and sounds like it is missing. The plugs and wires are new and the MAF and throttle body are clean (cleaned them recently). It is not throwing any codes either.

It only does this when sitting overnight, not after sitting during the day while I'm at work. If I'm out running around it runs smooth and doesn't do it if I make multiple starts and stops throughout the day.

I'm thinking it's either the fuel pressure regulator or pump. Either way I'll have to replace the whole assembly.

Thoughts?

white1500 · July 24, 2014

I'm not sure if the gmt900's had this same problem but the intake manifold gaskets tended to go bad on ours. My truck has what seems to be the same symptoms as yours, rough idle when cold from overnight but otherwise she's at 100% the rest of the time.

Look up the manifold gasket issues.