1999 Chevy Suburban rough at start up?

[boogie_4wheel]

Probably have a leaking injector(s). As the motor sits, the cylinder gets filled with a little extra fuel. When you first start, all that extra fuel is getting burned out (what didn't seep past the rings and in to the crankcase). It will take a few revolutions of the motor to get burned out, then after a short running of the motor, it will operate fine. The 'spider' injection system is known to have leaky injectors. If this is the issue, it should be fixed, since the fuel leaking in to the cylinder will dilute the crankcase oil and that isn't good.

Pull the plugs and see what they look like. Any wet ones, or a couple that look very different than the others?

 

[minorm2]

What could be causing the rough starting of the engine? It almost feels like it has bad gas every time I start up in the morning, afternoon, or whenever I start up. Once I am on the go it seems to stop the rough ride....could it be a bad gas pump? Vortex in the intake manifold leaking gas? This is driving me crazy! It made some a loud bang/knock sound and nothing happened a week ago. It did this twice. On the third time it started but ran really rough...the whole truck shakes like crazy! Any thoughts???