1992 4.0 manual 4x4...
So I had a bad miss, new plugs and wires fixed that but it still had a little rough idle... it's gotten worse with a couple weeks so I went in to see about it... had a loose plug... so tightened it, which helped, but still not smooth... listen to the engine and I notice it making a rhythmic sucking from exhaust consistent with rpm... put a piece of paper up to the exhaust tip and everytime that sucking cylinder hits it pops the paper against the tip pulling it up not pushing it away... I've sprayed carb cleaner all around the intake valve covers and vacuum connections and there's no change in idle...
anyone got some tips recommendations solutions etc?

 

Reads like a burnt exhaust valve
The paper at the tailpipe tells the story

A misfire from bad spark or fuel issue won't pull the paper back towards the tailpipe, just wouldn't push it as far out
If exhaust valve is burnt(not sealing the cylinder) then on the intake stroke of that cylinder it sucks in exhaust, and the paper at the tail pipe

You can do compression test, or leak down, to find the cylinder, but would still need to do Valve Job on both heads regardless of which cylinder it is

 

Thanks for the reply
i was afraid of that vey thing and im pretty sure i know which cylinder just judging from the shape of the plugs that came out... so happens its the same cylinder the new plug loosened up in after i am certain i tightened adequately... in wondering if its got some trash in there jamming up that valve even...
again thanks for the reply