Random Cold Start Stumble & code for CYL 1 misfire

2012 4 cyl auto 88,000 miles ( only had it last 8000mi )
I just had a second event of a random (not every time) cold start stumble at warm 70F , throws code PO301 for CYL 1 misfire, and oddly there was also a traction control light but I don't remember seeing a code for that could just be because the engine is shaking so bad ,
I will start checking, intake vacuum at idle, compression and fuel pressure ?
I have a simple Innova Code Scanner but it doesn't do a whole lot of scanning
I will maybe try this first but i think it is unrelated
https://www.tacomaworld.com/threads...ibrate-your-vsc-computer-the-easy-way.467485/

I just did a level lift and got alignment which would explain the traction control light , but the cold start stumble check engine light PO301 CYL 1 misfire should be unrelated
I am suspecting a possible leakdown overnight of CYL 1 injector
Coil On Plug corrosion (less plausible because it usually exhibits at high rpm)
Worse case scenario would be a CYL 1 compression problem, which causes problems at cold start with the Idle Air Control device because it wont produce enough vacuum at cold start to open the door correctly ( or at least on the gen 1 4 cyl, it was the case )
I found another post from 2020 with the exact same symptoms but no follow up and no responses ,( I guess he got it fixed and didn't need our help anymore)
and this one related : https://www.tacomaworld.com/threads/traction-control-light-check-engine-light.837666/#post-29996604
I am just starting to troubleshoot, will let you know if I find anything

 

Trac Off light will always accompany a CEL on Toyota so disregard that until the CEL is fixed.

Are you losing any coolant?

 

not aware of losing any coolant .

 

Update :
went to the local Toyota dealer to see about getting a diagnostic and got to get an opinion from the Service writer with over 30 years diagnostic experience on Tacomas, its unbelievable what this guy knows, he said he thinks I am on the right track and if I want to save a bundle his opinion is to throw some plugs and even C.O.P. boots at it and try some injector cleaner, an injector could be getting sticky( way cheaper than the diagnostic alone)
said a low compression idle air control malfunction would throw ALL misfire codes ( as did my Gen 1 ) and low compression is not very likely at 88,000 and wont cause a cold start misfire.
If a spark gets weak on CYL 1 it can start showing up at cold start because the fuel enrichment fouls the plug and shows misfire
if it was a leaky injector it would most likely take longer to start
said same as DM93 about trac lite
also said don't worry about clearing the VSC computer unless the lite is staying on or causing issues after doing the lift but be sure to check that the wheel sensors wires are routed well and not getting yanked or stressed

 

I put in some BG fuel system cleaner snake oil ( $33.00 for 11 oz can ) drove it about 250 miles so far .
only 3 cold starts so far, but no more misfire at cold start (yet) .
It seems to idle smoother and have more power . It feels less sluggish (typical 4cyl) and the slight steering wheel vibration at idle is gone .
Time will tell if it is fully cured.
I do not like using additives because it can burn up the cats , but they swear it won't hurt , the Toyota dealer sold me the BG snake oil from their parts dept. If the Cats burn out within a year or so , I will blame the BG
I held off on changing the plugs because I did not notice any "pop" when it misfired which is what I usually experience from a spark misfire ( but still plan on getting around to it because it is up to 89,000 miles
so maybe it was sticky injector, I did not swap injector location to confirm, I just poured the BG snake oil in a 3/4 full tank and drove drove drove it so maybe I got lucky, it sure seems smoother now

 

I am declaring it fixed.
No more cold start misfire and it idles smooth, no more steering wheel vibe at idle

 

I take it back. After about 10 overnight cold starts , it happened again today.
..... re-affirmed my lack of faith in Snake Oil remedies. but at least it seems to idle smoother, or at least it feels that way in my mind, I could swear the idle is smoother ( but still not worth the $30)
I will try spark plugs but for some reason I am even doubtful of that
I found three similar threads of the same symptom "cold start Cyl 1 misfire code at random not every start and goes away after shut off and re-start", but none have a resolution or happy ending follow up post, and they had no luck at throwing plugs at it
I can find no correlation to the length of time sitting before cold start . Ambient temps have been steady , low 60's AM to 90's PM
Toyota tech suggested that a spark misfire can show up at cold start only because of combustion conditions
but I am doubtful
all my previous experience with spark misfires have involved a popping backfire at higher RPMs along with a miss at idle but this is just stumbling like a dead cylinder at overnite cold start only
I am suspecting a fuel pressure leak off because it recurrs only on cyl 1 at random and only at cold start, maybe swap injector locations if the old spark plug prayer fails

 

like perhaps a fuel pressure regulator malfunction ? seems it should act as a check valve to hold fuel pressure in the rail overnight
So that every time this happens it is like running it out of gas, and refilling and going through the stumble as it re-primes and maybe CYL1 is last in line to get gas ?
Such a problem would be almost impossible to confirm if it was happening at random and probably would not show up on any diagnostic machine or way to check it every morning with a pressure gauge

 

not that anyone seems to care, but I changed the plugs and nothing looked unusual at first except at close inspection I could see that cyls 234 each had only one tiny crater shaped indent in the ground electrode where the spark was jumping and were very eroded the tip looked wedge shaped and worn down at the end BUT #1 cyl spark plug looked different, more built up on the ground electrode than eroded like the others, with something resembling welding slag and with 3 or 4 craters, like the spark was jumping around hunting for a ground
so maybe it was plugs after all
It started and idled higher than usual this AM after sitting overnite, no stumble , so far so good .
It also seems to have a little more power but that is a subjective obs

also discovered there is a check valve inside the fuel pump that (potentially) could leak down overnite , but hopefully it was just 80,000 miles on the plugs

 

If you were getting a misfire reported on cylinder 1 only, the things you’ve considered that would affect all of the cylinders don’t seem as likely as a plug, coil, or injector. With new plugs in there, it will be interesting to see if the problem has been solved. Please do report back with your findings; if there’s more debug needed, I’m sure additional suggestions will be forthcoming.

 

Misfires (especially intermittent ones) are one of those things that's very difficult to diagnose over the internet, aside from the easy checks like inspecting/swapping plugs and coils, checking compression, or checking for coolant leaking into a cylinder.

Beyond the easy stuff it's hard to describe what to look for and check and alot of stuff you need specialty tools to check that the normal DIY isn't gona have or want to buy.

In any case it sounds like you may have found the culprit of your misfire, without seeing the plug it sounds like that cylinder may be burning oil leaving chunky deposits.

 

So far only about 3 perfect cold starts to report but it is starting and running profoundly better than ever since I have had for 10,000 miles, I bought it cheep as a theft recovery with no damage or missing parts and the carfax showed long periods of low mileage and lots of dealer service. It cold starts and idles smooth at 1100 now instead of 800 and slightly shaky like it was, and before it was sluggish on grades and kept falling off in rpm and downshifting, I figured that's just how it was going to be for a 4cyl with a 3 spd auto , now it just holds the rpm on most grades Throttle response had a lag, glad that is better and shifting points are better feels more peppy overall so I figure that the plugs made all the difference, im not an expert but the plugs do not look abnormal to me, no soot or goo just cinnamon , other than the typical eroded ground electrodes from so many miles the fuel system cleaner may have helped a little.
it was just ok before but its like a different motor now, glad it wasn't how it was supposed to be