Tacoma running rough no CEL

Also, you may be onto something here with the plug wires. I forgot they share a coil pack between two cylinders and have a plug wire connecting them. After I sold my old T to my nephew, he had a misfire problem and it turned out to be a bad plug wire.

 

It’s worth trying it, they were off and on a couple times and seem kinda twerpy to begin with....

 

Cranked it up and let it idle this afternoon and it was not missing a beat. So I took it down the road a couple of miles and back and still running good so I left it running while I put some things up. Came back around house and it was missing.
Picked up one of those "FIXD" code readers and decided I would try it out. Showed misfire for #2. By that time it was good and dark so I popped hood and looked real good and didn't see any arcing. Went in house and got spray bottle of water and misted all over the wires between #5 and #2 and nothing.
I also picked up a set of spark plug wires but did not swap them out tonight. Was going to get a set of coil boots but they only had 1 so I will at least change the one on the #5 cylinder and pick the other 2 up next trip

To answer a few questions:
Spark plugs are NGK dual electrode
Truck has 297K

 

Plug I pulled when this started, may be on the lean side after looking at google images and comparing?

 

Plug doesn’t look bad but it’s hard to tell whether or not there is a warm color cast to the photo making it look particularly tan. Side by side comparison to another plug would help if you want a more definitive read on the plug condition.

Sounds like the plan is possibly new wires (your call, obviously) and a new injector (hopefully arriving soon). Based on your test, wires might be ok, but on my 2.7, the plugs and boots are recessed in the valve cover and not exposed, so arching wouldn’t necessarily be visible. On my old VW, I could pretty well see where the plugs threaded into the head, along with the entire length of the plug wires, including where the boots attached to the plugs, so any arching was easy to spot. Not sure how it looks on your 3.4, so I don’t know if your test is definitive; visual inspection would NOT be definitive on the 2.7 due to the hidden boots.

When are the injectors supposed to arrive?

 

If time permits the new boot and plug wire are going on this afternoon/evening. Rule that out and other 5 plugs, wires and coil boots getting changed when I have intake off

Injectors finally made it but not tearing into all of that until I can knock most of it out in one session, don't want to leave top end open any longer than necessary sitting in the drive

 

I hope this solves it. Boots and wires aren't terribly expensive and they do need to be replaced on occasion. I've been advocating for a likely ignition issue throughout this thread, and I want to be right, but not as much as I want for you to get the issue solved. If the ignition parts don't do it, then I think investigating the fuel supply to that cylinder is the next step. Fingers crossed.

 

Kinda skipped through the thread. Did you try moving the coil to a different cylinder and see if the code follows?

 

I think he swapped in another coil and the problem persisted.

 

Andy, does a miss always get recorded? Mine misses but have never ever got a fault or CEL for it. Thanks

 

I don’t know for sure, but I suspect an occasional random misfire doesn’t reach the threshold to trigger a CEL. They probably happen more than we realize.

 

Andy is correct, I had another coil that was known to be good and swapped it in

I don't think all misfire codes register (or whatever the term is) as several times with it running rough and no CEL I have had diagnostic devices show codes

Got home and cranked it up and let it run until it started to miss. Turned it off and swapped the plug wire from #5 COP to #2 cylinder. Cranked back up and no change. Cut it off and changed boot on COP, cranked back up and still missing.

So I have eliminated (in my mind) MAF, plug, wire, COP boot, sprayed a bunch of carb cleaner and pretty sure no vacuum leak. Also compression test which showed 208psi.

I have new set of injectors in hand but would like to figure out where cam position sensor plugs into harness for 2-4-6 bank to check resistance and maybe check crankshaft position sensor before changing injectors (just because I could return them for refund if it was one of the sensors)

Good thing is I have gained some more knowledge related to figuring out causes of misfires

 

Well, if it’s not ignition related, we can be a bit more confident in the injector hypothesis, which would mean you’re not harming the catalytic converter with raw fuel, so that’s a relief. Not sure I follow the cam position sensor theory. Doesn’t hurt to check, but if that were the issue, wouldn’t it miss on other cylinders too?

 

Just remembered this thread: https://www.tacomaworld.com/threads/high-compression-in-4-cylinder.709279/#post-25208986

Didn’t you state the compression was above 200? Can you check the other cylinders before we get too far along? Not sure why high compression would trigger a misfire, but it makes sense that preignition would be worse in a hot engine, no?

 

I believe the cam and crank and cam sensors do play a role in fuel delivery. If one is flaking out.... trouble is you need a decent scanner or oscilloscope to read the wave. Funny this got brought up cuz it crossed my mind earlier. They are relatively inexpensive...

 

Maybe it is missing on multiple cylinders.... tough to tell from the drivers seat

 

Multiple misfires should trigger multiple misfire DTCs. OP only mentioned miss on cyl 2. Do we make anything of the high compression value? Hard to tell without numbers from other cylinders tested at the same time.

 

When you're checking cam/crank sensors also check the resistances of the injectors like I mentioned earlier.

 

This where I got idea about cam and crank sensors, right or wrong I don't know?

https://www.700r4transmissionhq.com/p0302-toyota-tacoma/

Followed link and will check all cylinders for compression and report back

99% sure misfire is isolated to the single cylinder, if COP is unplugged from harness truck will only run a few seconds

DrZ the idea of checking sensors is the thought they are easier to get to than the injectors but I promise if I get deep enough in to check the injector resistance I definitely plan on doing just that along with any further investigation necessary to ID root cause

My ultimate goal is to ID cause and post what I found so that maybe it will help anyone else who has similar problem as well as those who have helped me be able to help others who come alog with similar problems

 

Oh yeah, I forgot the injectors are not as easy to get to on the 6-cylinder compared to the 4-cylinders. I'm not familiar with the details of the 6-cylinder, but there must be a connector on the harness leading to the injectors that's accessible. If you have a wiring diagram with the pinout and wire colors leading to each injector you could test from that point rather than directly at each injector.