2002 dodge ram 1500 conversion van with a 5.2 V8 133k

My van misfires and backfires thru injection once warmed up. It will only do this under throttle. I drove a 2300 mile round trip this summer and acted up the whole way.

I can drive around town anytime and is fine. Once it is warmed up, when you push the gas just a bit, it will buck. New wires, cap, and gas cap. When I took into the shop, they did not see my problem because they didn't drive long enough.

I am the 2nd owner of the van. Have code showing misfire on #8 plug but cannot get it out. Only been able to get #6 out so far. They are the original plugs im sure.

Could the plug be causing all this? Why does it run fine around town?

 

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The heat shield is probably holding your plug wrench off the plug. The shields can be removed carefully with chanellocks. Spray your lube of your choice, then squeeze the sides opposite the seam, and wiggle it out. My 110k mile Champions were gapped around .085, looked like the electrode had just burnt down that far. At least 8 is about the easiest to get to. Probably not the problem, but needs to be changed anyway.

 

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Your plugs have probably never been 100k plus between changes and you live in texas where rust is a non issue. I assure you I have and tried some quality (Snap On, Matco, SK) thin walled sockets, and even took a grinder and made a very thin pointed socket from a cheap Kobalt, no go on 3 of them. I have seen several post here where all heat sheilds have been removed some even running headers w/o issues. One other thing to consider is if the plug wrench is hard to get on the plug, you are likely to displace rust particles if you do manage to get it on. As soon as the plug leaves the hole, the particles enter the engine.

 

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Plug changes are easy once you get those useless tubes out of the way. One other thing to consider with the rust is it forms on the inside right where it enters the head, if allowed to continue they can and will break off even with the head, ask me how I know. I say get them out while you can if salt is used in your area. I can only see more chance for contamination by removing valve covers, the 1&3 you mention are cake if you remove the front left tire.