Plug Wires Arcing, Misfires in All Cylinders, and System too Lean help

Hi all, this is my first post on here, so please let me know if I'm out of line on anything.

My truck is a 1998 Tacoma SR5 with the 2.4L and 5 speed manual.

Context: About a month and a half ago, my headgasket blew due to overheating, so I changed the headgasket and thermostat. After that, it still wouldn't run, so I took the timing cover off to verify my timing (luckily is was correct) put everything back together and changed my Sparkplugs after that, it ran, but very rough. I cleaned the throttle body and MAF, changed out the upstream 02 sensor, still no change. The other night, I watched it run in the dark and, sure enough, plug wires were arcing all over the place. So the day before yesterday, I replaced plug wires, coil packs, and relocated the ground wire for them directly to the head via the oil dipstick tube. Last night, they were still arcing, even onto my hand when I touched them, so today I double checked all if the grounds to them, and they were all good, pulled my sparkplugs, and they looked like it had been running SUPER lean. I also listened and heard all 4 injectors working.

CODES: System too lean
Random Misfire p0300
Misfire on 1,2,3,4 p0301-4
O2 Circuit slow response (hasn't come back since replacing the sensor)
O2 Circuit bank 1 sensor 1

LIVE DATA: these are all at 850rpm and 175⁰
STFT: 19.5%
LTFT: 19.5%
Spark Advance: 17.0-18.5
MAF: 0.73-0.81 lb/min.
IAT: 111⁰F
TPS: 11.8%
02 sensor 1: 0.000V
STFT: 0.0%
02 sensor 2: 0.040V
STFT: 99.2%
I am by no means an expert, and any help is greatly appreciated!

 

Have you checked fuel pressure? Also...checked compression?

 

I haven't, yet, going to see If the ones my local parts stores rent work with banjo bolts(for the fuel pressure) while I'm there, I'll go ahead and grab a compression tester

 

That's where I would look next. Low fuel PSI and/or low compression can lead to lean conditions.

 

Okay, so I did a compression test, and all of the cylinders had good compression.
4: 170
3: 165
2: 170
1: 175
Then, I did a fuel pressure test. The pump didn't cut on until I tried to start the engine, but then it held 45 psi across the board (idle, revving, constant high rpm) from what I've read, this seems to be normal.
Not sure what else to do, honestly. I'm kinda at my witts-end lol.

 

Hmm. It might be worth trying your old coils and wires.

 

Alrighty, swapped those out yesterday, still no dice. Just finished putting the new ones back in again. I was looking at a wiring diagram to them, and the Black/red wire is shared between the coil packs and fuel injectors, so I think I'm going to follow that and see if there's a break or something wrong with it.

 

Any progress?

 

Yes, I checked for continuity on all of the wires, then checked to see if any had grounded out, they're all good. After talking with some buddies of mine, we figured even though the injectors are all "clicking" and are reading proper ohms, they could still be clogged up, not flowing correctly, improper spray pattern etc. When I pulled them off, the nozzles themselves looked pretty gunky (not sure why I didn't check them when I installed them the first time), so I sent them off today to GB Remanufacturing to get rebuilt.

 

Interesting. I had thought to mention injectors but since it ran before seemed like a longshot. But it sure doesn't take much for them to underperform. I am a huge fan of having injectors professionally cleaned. I have used witchhunter.com for decades and the results are always surprising. But the arcing sure seems to be very unusual and I can't see how a lean condition could cause it. I hate to even ask this but are you sure the ignition wires were actually metal on metal at the plugs? I am sure you checked but when engine issues get weird it is always good to assume nothing.

How were the injector o-rings? Huge potential issue there.

 

It's funny that you'd ask that, because at first, when I had just finished putting it all back together, I actually didn't have the plug wires pushed all the way down onto the plugs , but yes, thay are pushed all the way down now. As for the O-rings, I had just used the cheap ones that came with the headgasket kit, and when I pulled them out with the fuel rail, I realized some of them were actually loose and wobbly because 2 of the 4 o-rings were a bit too small. This rebuild company includes all new o-rings, so I'm hoping there's are better quality than the ones I used.

I doubt this will fix the plug wires arcing, but I'm hoping it will stop it from running lean atleast.

 

I just realized that I eventually figured out the problem, and never posted what it was. When putting the intake manifold back on, the manifold gasket wasn't on one of the studs coming out of the head, causing a massive vacuum leak. Once I found this out, I replaced it and it ran like new!