Yeah, I have 0 desire to drop the tank myself and I have never seen an access port in the trunk, that would make things too easy.

I will post up a short diagnostic tomorrow and an after fri night or sat. Depending. Apparently the Bosch O2 sensor I bought has no pigtail so I have to splice it in...

 

So I replaced the forward row of plugs and the upstream O2 sensor, then the weather hit and I decided that working in 19f weather was not something I wanted to do outside . A 180 mi round trip. Put my gas milage as "improved" from 17.5 to about 24 but I was still showing multiple random misfires and a terrible loss of power. As in I could not maintain 50mph going up our local mountains.

Today it was warm enough after class that I decided to replace the back plugs. I popped the cowling off in the campus parking lot, grabbed my tools from the trunk and suddenly learned that I wish I had pulled the cowl to replace the O2 sensor. It would have saved me a lot of lower back pain and time.

Anyway on the drive home, up and down our mountains (Appalachian foothills really) with a bad battery, almost 40 mpg (39.8) that may be the best I have ever gotten in that stretch.

Now I am still showing p0420 decreased cat efficiency and P0A7F (aka go spend 2500 on a new battery) but I had all 4 gerbils running fine and no other issues. So I was right. The O2 was causing rich conditions and given the back plugs we're denso and the front were ngk I am going to believe I was on the original plugs at 196.5k miles. Dunno how long they should last but 200k on factory original plugs? Color me impressed.

 

Glad it's sorted. I was really concerned something else was going on. Must have been a cascade of issues.

It's possible they were the originals. Both of mine had that config when I replaced them. The second went to about 210K miles before it got misfires, bad cat, bad battery, etc... (like yours).

 

Thanks for your guidance as ever S. Keith.

 

Heh... FWIW, you're welcome... mostly just guesswork at my end... you did all the hard stuff...