ignition woes misfore with codes

[Nullifier]

Ok guys I have a '97 w 4.0l and 126K on the second motor. It has been running great after a tune up a few months back and I got in the truck sat and bam it was running rough off the start and under load getting up to speed it would miss fire really bad shaking the whole truck. Under load it is an inconsistent miss but I would say it misses every 3-8 seconds At idle it just runs rough. Any way I checked the fuel filter, plugs and wires are all good. My scanguage shows the following codes P0303 (misfire @ #3) P0171 and P0174 (system adaptive fuel to lean Banks 1 & 2). it is the later codes that scare me.

Now on the first engine at 118,000 miles I had an intake valve on the #3 cylinder seat itself into the head and it was sticking. Fuel was not entering the cylinder properly and a "miss" was the result. This feels the same but I am hoping that is not the case, although the Lean adjustment is pointing pretty hard to the same issue. I can always hope for a bad ignition module but is there a way to test those out before replacing? I'm open to other suggestions at this point.

 

[MAKG]

A miss can cause lean codes all by itself.

 

[Big Jim M]

Missfire on #3 is a good sign the plugs and wires are NOT in good shape! I'd start by putting at least ONE wire and plug in it..
Also as a side note.. Valves don't "stick" the camshaft WILL push them open! Now if high revs have BENT the valve shaft they may not go all the way closed.. In which case if it is an intake valve the fire will enter the manifold out of phase and burn the fuel meant for other cylinders.. causing a really BIG miss. And the computer will prolly read "a lean condition for other cylinders".
Big JIm