Take a look at my post earlier today. I had same basic issues and it turned out to be a slight crack in the porcelain part of the spark plug, which expanded after it got to operating temp causing a grounding.

 

Thanks, I already tried 2 new plugs.
My friends tenant had the same exact thing and he ended up having to change the spider.

 

If you want to use misfire detection to identify a particular cylinder's misfire, I would first make sure it can correctly identify an induced misfire. Misfire detection system can get screwed up. So pull a plug wire on #5 and watch the LIVE misfire counts on your scanner - they should count up rapidly for #5. Now put that plug wire back on and switch to another cylinder. If misfires are counted correctly on both cylinders, then and only then can you trust that your misfire is on #5.

I really doubt if the spider is your problem. With the cost, I would want to be a lot more certain before replacing it. Sounds electrical to me. Too bad no one has oscilloscopes anymore. Would take less than a minute to clamp the leads on and ID an electrical problem in secondary ignition system while the misfire is present.

 

Ok so I may be going crazy working on just #5. Time to regroup the brain.

Thanks Les

 

You are welcome. Best wishes for a successful repair. Let us know what you find out. Do you have a scanner that can read live misfire data (not just a code reader)?

 

Have you tried running it at night and looking around on plug 5 for electrical arcing?

 

Nope but i can borrow one if need to

 

I will tomorrow night, its raining at the moment

 

Actually might be better to do it with the moisture in the air. Either way, you want to mist around the area with a spray bottle to better see any arcing.

 

I pulled off #5 wire from cap and the engine ran the same. Now its definately that cylinder and getting closer to being injector problem or not sure anymore.