Tacoma Cylinder 4 misfire…gah!

Hello!

Have a 2005 2wd Tacoma 2.7L 4 cyl with 267,000 miles, 5spd manual.
A few months back I started getting a PO304 code for cylinder 4 misfire. Along with that, the idle was Not as smooth as it usually was especially on a cold start.

I replaced the spark plugs and the misfire came back.

I then put a new coil pack on cylinder 4. Still misfiring

Did a compression test just to be sure and everything was fine there thank goodness.

I actually also got a new battery because that one was quite old and they misfire code actually went away after I put a new battery in, but I noticed that the idle was still a little bit off, even if the code wasn’t getting thrown. But I just left it at that because it was smoother and no code.

Fast forward about 3 to 4 months with no more codes getting thrown, And this week PO304 is back! And the idle is not great. I mean, most people who would ride in my truck wouldn’t notice it, but I do especially because it’s a stick shift and I can see the stick shift wobbling/vibrating around like crazy because of the rougher idle. So I’m guessing that this is a fuel injector issue? If not that what else could it be?

any suggestions greatly appreciated thank you!!!

 

You did a compression test...but did you do a Leakdown test? Possible to have a blown head gasket if it miss's on cold start..

 

No I did not do a leakdown test. Thank you for suggesting that. I just assumed since coolant level is stable and oil is clear, no white smoke that I was ok, but I suppose if there is a very small tear that would be enough to throw it off?

 

Yeah...it could be still be an injector,but a leakdown would rule out the headgasket.

 

Thank you I’ll look in to doing that

 

I don't know how hard the injectors are to get to on the 4cyl, but IF they are easy, you could try swapping 3 & 4 and see if the misfire moves with it.
Disclaimer: I know this is some redneck crap, and you'll likely tear or destroy the o-ring, but maybe not....just spit balling.

 

back to the basics...
you may have carbon tracked the ceramic of the new sparkplug cuz im assuming you didnt replace the coil boots along with the sparkplug?
coil boots are like replacing your sparkplug wires....

research carbon tracked spark plugs & wires...
Maybe toss another spark plugs at it, cheap enough...

always replace plugs & coil boots together.

 

ok im defintely going to read up on that thanks!

 

Yeah I thought of that too haha. But like you also thought of the o ring situation. Well my first plan is to change out the fuel injector on 4 on Sunday. So we will see how it goes!