Little help here?

So, I have an '06 Scion XA with 157k miles. Last night I did a 60-ish round trip drive, when I got home I was down on power and had a loud knock and smelled the car running really rich. This morning same issue, but a CEL on now, still need to borrow a scanner to run codes. So I pulled the plugs and found one with the strap gone entirely and 3 others in ok shape. What should my next steps be? Obviously new plugs, coil packs are original as far as I know so those probably need to be replaced to. I also did plugs 6 or so months ago with no issues till now. 

Buy ngk plugs next time. My experience has been that motor is more sensitive than most to plugs.

Plugs on my xB were a 30k maintenance item.  My moms xB lost its first coil by 100k and 2 more by 120k. The aftermarket replacements lasted @60k. I want to say there was a gasket leak that dripped oil in one of the plug cavities to blame for one, but I might be thinking of a different car.

I'd start with plugs and order a set of cools and go from there. 

In reply to oldopelguy (Forum Supporter) :

What about the missing electrode? 

In reply to oldopelguy (Forum Supporter) :

Good to know! Didn't know they burned through them so fast. Sounds like coils are well past their sell by date then too. Thanks for the help!

I don't have a good view of the gaskets, but that looks like the plug wasn't seated all the way.  No good heat transfer from the plug to the head can equal melty electrode.

Make sure the threads are all there and clean, and make sure the new plug is seated properly.

I'd second the NGK only comment. For some stupid reason every Toyota I've dealt with seemed super picky about ignition components. And test the coil from that trouble cylinder too. I'd fork out for the oe coil as well, but maybe I'm just paranoid. Or sell it and get a Honda. Only half kidding. Toyota rubs me wrong, can't explain it. 

In reply to barefootskater :

Good to know about Toyota ignition systems. Going to throw some plugs in today and order some coil packs. Hopefully that's all it is.

In reply to thedanimal :

Some of them use denso spark plugs. You'd think after 4 years of slinging Toyota parts I'd remember which went where but I can't. Either should be fine though. And I don't work there anymore or I'd get you the part numbers. 

We used to say at the garage where I worked, "Autolite, but they don't!" Second on NGK. Bosch good too.

Update! Put new NGK'S in and it runs great. I will be replacing the cyl 1 coil pack. I'm guessing it's a little worse for wear given how hot the plug got. But no knocking or crazy noises.

Strange how something so simple like spark plugs can be so different in each vehicle, but it's so true.  I treated my Impala SS LT1 to Bosch Platinums.  They lasted 14k before I started getting a misfire and found that one of them was just like yours; missing the electrode.

Back to ACDelcos and it was fine for another 50k when I sold it.

NGK works best in Toyotas.  I have used Denso with pretty good luck as well.  Unless you're driving a modified vehicle that needs a different quality of spark, I find that off-the-shelf stock part numbers work best.  Just replace with OEM which should be NGK.  If you were dealing with a V12 and plugs were $10 each, I might shop for the next best alternative, but we're talking about 4 plugs at $3 each.

From the looks of things to me, that one plug is seeing almost no fuel.  Bad injector or injector wire?  That might cause what you're seeing.  Minimal fuel in that cylinder could cause the knocking and down on power, then the other three are dumping extra fuel to satisfy the O2 sensor causing the rich smell.

In reply to Curtis73 (Forum Supporter) :

Going to run some injector cleaner through, didn't think about that. But something to take a look at.