I have a '98 ram 1500 4x4 with a 360. I bought it 5 yrs ago with 30k miles on it. As with all my cars I did a tune-up when I got it. All went well exept #8 plug was hard to get out. Every 30k miles arfter that I've had to do a tune-up for random misfire problems. At 185k miles it has gotten worse. It now runs rich as well. It runs smooth onlt on the hiway @ 75mph with no load. I changed the O2 sensors (2 of them). And 2 injectors (#1 & 2). My scaner is no real help either. I'm open to any ideas on where to look now.

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Check the plenum gasket. And do a search here for how to route the spark plug wires.

 

Is there a way to check it with out pulling the intake?

 

I have this exact same problem. I believe I may have a cracked head on #8. Have you run a full compression test yet?

 

Mine persistently had this problem for 10,000 miles off and on. The re-route TSB cured it when plugs, wires, cap, rotor, distributor and O2 sensors didn't. It's free and doesn't hurt to try.

Hope this helps.

 

+1 on trying to re-route your plug wires. I had the same issue, right around 185k also on mine, after trying all the over the counter remedies, I ended up running a compression test and found out that #5 cylinder had a bent exhaust valve. Cheap and easy to try, might be time for a new set of heads! haha

 

And as far as checking the plenum goes, just remove the air cleaner , open the butterflies and look into the intake with a flashlight and see if you have oil pooling .