Cyl 6 misfire 40-50mph, no code, slight oil on plug

I got a new-to-me 07 4.0 V6 a year ago with about 180k. Plugs hadn't been changed in who knows how long and misfired badly on uphills. Prev owner told me coils were changed a year prior (2yr old now) with Densos. I put in new OEM copper Denso plugs and it fixed it right up. Been driving it for the past year with no other issues.

It's been a year now and I am getting more frequent misfires on cylinder 6 around 40-50mph. Shows up on slight uphill grades if I'm in 5th, have to brake and try to speed back up. Seems to be eliminated if I pop it over to 4th overdrive.

I verified this is a misfire and not transmission related since I have a bluetooth OBDII reader which counts cylinder misfires while driving even though no code is thrown.

On my trip home today from the shore (4hr drive) I accumulated about 27 misfires on cylinder 6. Idle and cruising at highway speed no issues.

When I got home I pulled the plug and noticed a little bit of oil around half of the edge of the plug, but it wasn't super oily--only one side. Perhaps oil seals need replaced...but would that even cause this misfire or is it probable it's unrelated? I swapped the coil pack from #5 and #6 to see if the problem follows and will report back tomorrow after my commute.

I was initially suspecting injectors since I haven't touched them and there's no maintenance record of them ever being changed...but it's suspect/unlikely since it's mostly tied to one cylinder. I get an errant misfire on another cylinder every once in a blue moon but not common.

Hoping someone with a bit more experience could weigh in..

 

Im pretty sure that oil is external, leaking valve cover gasket / tube seals....
Cool to know toyota does misfire count, ford does...

Shouldnt be driving it at all with every occasional misfire, youre wiping out / damaging your cat converter.

 

Electrode looks good, maybe a little wear but oil could just be from valve cover. Doesnt look like its burning oil. My .02cts.

Swap coil location, see if it follows.

 

You might throw a bottle of Techron fuel injector cleaner in it too.

 

I'd like to see the fuel trims on bank 2 when it happens.

Even looking at the LT now, might give you (us) a clue.

 

Good data! Need input!

 

As suggested, Share some more data, swap parts side to side, and post updates. You sound like you really want to fix the issue not mask it.

That's not a lot of misfires so it may be somewhat hard to track down. It's not throwing codes because there is a threshold for code set criteria.

 

Here is some data for Catalyst damaging misfire, looks like they're suggesting more than 77 per 200 revolutions is considered damaging (CEL blinking). I don't believe 27 misfires in a 4hr drive would be considered damaging.

 

It all adds up and it doesn’t just take a flashing check engine light to cause catalytic converter premature damage…..
What do I know,
Tell that to all these customers in just 1 months time, they thought the same thing…
All customer pay at about $2k+ with labor & then some…
End of the day, it’s a costly part, not worth the risk…

 

This right here actually does kinda confirm it's a torque converter lock-up issue. Some guys have had luck adding LubeGuard

27 misfires in 4 hours? That's nothing. 4 hours is a long time.
That shuddering feeling in 5th, if that was a cylinder misfire you'd see that counter go up to 30-50 in less than 10 seconds. Look at the counter the next time you feel the shuddering in 5th and see if the numbers are climbing rapidly

 

Whatever you gotta tell your customers to make a buck and meet californias strict CARB laws. I'm just sharing what Toyota says is damaging to catalytic converters.

 

The book, the manual, & real life reality are 2 different worlds....
minor misfire or severe, should just be kicked down the road cuz you cant figure it out, you dont want to pay a pro to figure it out, its no convenient, etc....
All these cats were replaced due to p0420 / p0430, has nothing to do with "california"
A CEL comes on just the same on a New York vehicle as it does on a California vehicle so not sure what ca & carb has to do with anything.
or me trying to make a few bucks....

Im simply trying to point out, dont kick it down the road & drive it while youre trying to deal with it cuz you dont have another means of transportation, not the best approach....
youre not wiping out a $75 part....
Look at all the p0420 p0430 posts on here as it is, theyre not bullit proof to begin with...
Just saying....

He driving it now, it gets worse & he continues to drive it then too..
See it on this forum all the time....

 

To figure it out it needs as suggested coils,wires,plugs swapped around to find what moves the problem. No one is saying he should continue driving millions of miles on it like it is. I have chased p0420 and p0430 codes on my truck with 343k miles, have not damaged the cats, and have corrected the issue without buying new cats. We're here to help OP, not lead him to buy new cats.

Just for reference CA and NY have the strictest emissions laws in the US. Just saying...

 

What is a good scan tool to detect misfire?
I'd like to keep one on hand.

 

A good scan tool is Toyota Techstream on a laptop. Can get possibly dodgey versions of techstream on Amazon and lots of car diag websites for reasonable price.

If you have android check out the Torque app and a bluetooth dongle. Even if it's not in live data, you can see them under the Mode $06 tests.

I also have 2 Foxwell diag tools that work pretty well. You can get them for 1 manufacturer or multiple, that cover a select few systems to all systems.

Youtube SouthMainAuto Uses Autel and HF Icon with different levels of success on different manufactuers, but those are pro grade expensive tools.

 

I wonder if I should revisit this theory... I did days of research when I first got it doing all major tune-up items and the last was doing drain & fill ATF... but GearCruncher and TheCarCareNut (Toyo mastertech) directly contradict eachother. Both ran shops supposedly. I am not ruling out torque converter shudder. But the "safe" advice (other than GearCruncher) is to not touch ATF if it hasn't been changed..ever. I can't afford to replace the transmission so I decided to just leave it as-is since to my knowledge it's never been changed. Car Care Nut's final advice is--either keep up with ATF changes, or don't touch it because of the variable valving that accounts for wear in the fluid. Fresh detergents in new fluid will change the valving supposedly. GearCruncher also seems bent on adding LubeGuard to burnt out ATF won't do anything. So here we are.

It's possible this "shake" I'm attributing to misfire is something else totally unrelated. It shakes a few times like it's either missing or struggling to get into gear. My only data point so far is when I feel the truck struggling (lugging down) 40mph and stumble, then refresh the non-continuous monitors bank on my OBDII app the Cylinder 6 misfire data is usually 2-3 counts higher.

Is it possible the torque converter lockup/shudder is lugging down the engine and the misfire is a symptom of the transmission bogging the motor down to the point of it struggling to stay in-time? (If things like VVT solenoids/injectors are already nearing the point of replacement)

CCN on Toyota ATF: https://www.youtube.com/watch?v=jJr30r6RRgw
Shudder: https://www.tacomaworld.com/threads/2nd-generation-transmission-shudder.808889/

This is what I bought:

$15 Veepeak Mini Bluetooth OBD II Scanner for Android (Incompatible with iOS), Car Wireless Check Engine Light Code Reader OBD Diagnostic Scan Tool

https://www.amazon.com/Veepeak-Blue...750688410&sprefix=obdii+reader,aps,126&sr=8-6

This is the app I use: https://play.google.com/store/apps/details?id=com.ovz.carscanner&hl=en_US

It's way better than the torquePro app. Less shiny and pretty but no-nonsense raw data readouts.

 

That looks like everything that Torque can do

Post up some more data as suggested. Pick an avenue to chase, swapping coils(Cyl 6 to the other bank) would be easist and report back.

Does the lugging feel like a complete loss of power? or intermittent? I had an issue where it felt like I was letting off the gas briefly and right back on the gas constantly if I didn't change pedal input on just the right hill grade and engine load, then getting p0420 and p0430 codes. Downshifting manually or giving more pedal input made the issue go away and start pulling as expected. That time turned out to be low fuel pressure.

 

I’ve always seen some logic flaws with the idea of not touching the fluid in high mileage transmissions. Not saying it’s wrong as I know there is plenty of anecdotal evidence of messing with it causing issues, but some of the arguments against don’t make sense to me. I’m currently running an involuntary test of the theory because a line pressure solenoid that had to be replaced on an A750F of unknown history…only about 1k miles in, we will see.

 

What I'm saying is, when you feel the shuddering in 5th gear, look at the misfire counter. If the shuddering being caused by a misfire it will count up quickly. Like up to 30-50 (or more) misfires quickly. When the shuddering stops the misfire counter will stop.
Like I said 27 misfires in a 4 hour drive is nothing, that sounds like a pretty healthy spark ignition system. And you don't have any misfire codes getting stored or a CEL coming on and flashing.

The concerns about damaging a transmission from changing fluid are a bit overblown. That is from back in the 80s and 90s when transmissions used to fail more often. These 4.0 liter automatics are stout and reliable. Gearcruncher knows his stuff and does this for a job daily. The car care nut is a youtuber looking for clicks

 

Sorry for the long delay in follow-up. I haven't gotten a chance to really take it out on a longer than 10min drive until this week.

Despite everything tried above: swapping coil packs, and plugs with another cylinder same issue--stuck on cyl 6. I am not convinced it's a transmission shudder, though. Everyone who describes shudder describes it as a "rumble strip" and this is more of a hard lurch or "trying to get into gear" less than a vibration. Still, no codes.

When I get the hard-lurch feathering throttle uphill around 40-50mph if I refresh the OBDII scanner I can see the "MISFIRE COUNT CYL 6: " go up by a single count. If I keep on the light throttle, low RPMs, and it keeps lurching over and over again I can see the misfire count on cyl 6 go up by single digits for each time it lurched. If I floor it and force it to downshift into 4th it will stop or if I pop it over to OD4 it goes away.

This is what's baffling me. Doesn't seem to be related to electrical/ignition. What's more, it doesn't seem to do it under same conditions when engine is ran <10m (I have a short commute). It starts behaving ("failing") reliably under these conditions after about 20+ min of driving when everything is good and warmed up. Would this point to a transmission issue? If so, how could that cause the cyl:6 misfire count to crawl up by single digits correlating to the number of times it shook?

Again I'm no expert and grasping at straws here but I also struggle to think it's injector/fuel related because I would think I'd see this happen under "normal" steady-state conditions if the injector was clogged/failing. Not just low RPMs in 5th and/or other cylinders misfiring if it was a fuel pressure related issue.

Very frustrating!