Having a persistent rough idle issue in my 1998 B1500, with the 5.2. When I drive it on the highway, it has good acceleration and power. I took it up on the interstate and it had no problem maintaining 75 mph. But in town driving it will have slight hesitation, and has rough idle. All underhood sensors (including oxygen sensors have been replaced, no check engine light or stored codes. Intake gaskets also replaced. Engine compression is good.

What could be causing this?

 

Injector cleaner, iac cleaned, throttle body cleaned, new spark plugs, cap and rotor. Anything related to a tune up would be where to start

 

I cleaned the throttle body, has new plugs wires cap and rotor. I put 2 bottles injector cleaner in it, , New IAC,TPS, MAP, coolant temp sensor, air charge sensor, both Oxygen sensors
also cam and crank sensors

 

What plugs did you install?

 

1. Test fuel pressure
2. Do either a compression or leak-down test.

 

I installed Champion RC12YC4, as called for on the underhood label.It had Champion #7436 platinums when I bought it

 

Has new pump/regulator assembly. Pressure good. Compresson 115 psi all cyls. Very odd issue, as when I tromp down on it it takes right off with no hesitation and good power

 

Might start checking for vacuum leaks. They would be more noticeable at idle.

 

That's what I was gonna check next, maybe there is a broken vacuum hose/line somewhere. I can rule out the intake gaskets as I replaced those

 

Did you address the plenum plate when the manifold was off?