cylinder 1 misfire help 2.7 2011 260,000 miles

hey everyone haven't been on in years. my truck is pulling up on 260,000 miles and im throwing a p0301 (cylinder 1 misfire)

I've replaced all spark plugs with ngk (gapped .44)
I've replaced coil pack and swapped it.
I've used fuel injector cleaner.

not sure if i should swap the fuel injectors or if this is an ecu problem?

symptoms are... Hard start for 1-2 seconds. then idles good and runs good under load.

any help would be appreciated. thank you again

all the mechanics are surprised I've put so many miles on it lol

 

or
maybe try seafoam?

 

Have you physically checked for spark at the plug?

Also, does this ONLY happen on start up?
And does it NOT misfire after start up?

 

Have you ever replaced the valve cover and spark plug tube gaskets?

 

neither. the coil pack comes with a tube gasket if that's what you're talking about.

 

yes only at start up! super weird. i def have spark at the plug it would shake like shit if i was running off 3 cylinders, right? but have i phsyically checked it with an ohm reader? i have not. i just figured it would shake all the time if that was the case.

 

and only for the first second or so^

 

Hard starts typically lead me towards headgasket leaks.

Pressurized coolant slowly leaks into the cylinder and fogs it up, it is very slow, but causes a rough start and the engine light to come on.

It's tricky to diagnose, we usually use a camera to watch it happen.

 

would i see coolant buildup ontop of cylinder by using a boroscope inside the spark plug opening?

 

It usually appears like a fog, you have to reference a good cylinder vs the bad one.

Sometimes there's droplets, but usually thats later on when the headgasket is properly leaking.

 

without knowing the actually problem, would you throw some headgasket leak sealer in it or any cheap remedies? not super mechanically savvy just handy

 

I'm a professional and I would sooner deal with having a rough start before I poured in the stop leak. It causes a lot of other issues with the cooling system.

We don't know if it is a headgasket, but they don't get better, you can usually spot a puff of white smoke on start up as it gets worse.

It could be a valve wiring etc.

ECU is least likely. I have changed very few Toyota ECU's in my career. They are near infallible.

 

ok thanks, appreciate fast response. is the spark plug harness the same wires that lead to the valve wiring? is replacing the harness even a thing?

 

Sorry missed a comma

Valve, or wiring. Burnt valves can be spotted with cameras as well. Less likely.

Wiring can be detected sometimes by wiggling the loom and connectors along the path.

 

Does the coolant level drop slowly over time?

 

The valve cover has tube gaskets

 

I got the same problem with mine. I have low compression on cylinder 1. Could be lots of things running from valves or piston rings needing to be replaced. I'm having a mechanic tear into mine Friday to find out what the problem is.

 

the coolant reservoir doesn't get lower.

i figured if i have/had low compression in cylinder 1 i would feel; but then again what do i know. lol

but ya i should really test the compression for cylinder 1 to be honest. or at least take an ohm reader to my harness.

pulled battery to clean throttle body and the check engine light came back after just 12 miles.

 

Step 1 compression test. It's free if you rent the tool. Or just buy one for $20.

 

wanted to thank everyone. i managed to get rid of the light with some fuel injection cleaner. with this market im going to sell it while it still runs. 260k on this truck as a second owner has been a mile stone.
just ordered a 2022 tacoma trd sport. thanks again everyone