I have a 1998 3500 with the 5.7. It just started running rough a few months ago and I find what is causing it. The plugs on the passenger side of the engine are all fuel fowled and it is not trowing out an error code. I have changed plugs, wires, cap and rotor. I even pulled the heads and had a valve job done. All oxygen sensors have also been replaced.

I am pulling my hair out trying to fix this and am out of options. I can't afford to take it to the dealer and need some advice. Thanks in advance.

 

Did you check the upper intake? Those plastic manifolds had a tendency to stress crack and caused a rough running condition.
Never heard of all the plugs on one side fouling, but it is possible due to too much air entering and the O2 looking for more fuel.
Try carefully spraying brake cleaner to try to find a leak while the truck is idling. If it appears the upper intake is cracked, there is a nice selection here
1998 Chevrolet K3500 Engine Intake Manifold - Delphi, Dorman - TheAutoPartsShop - TheAutoPartsShop

 

I'll try that. Thanks for the tip.

 

I'd think that since he pulled the heads the intake gaskets would have been replaced?

 

No leak in upper intake. Back to square one.

 

Check the spider injection, wont throw a code an the injector tube could be worn out or partical plug.