Intermittent P0305 Cylinder 5 Misfire on 2014 Tundra

Hi everyone, I've been having an issue with my 2014 Tundra Platinum 5.7L 104k for the past month. Long story long... I had the truck in for an oil change and engine air filter replacement, the next morning I drove it about 10 miles to work no problem, then started driving home that evening and it began shaking within 100 yards and the check engine light started flashing. I took it to Napa and it was the p0305 code. I bought 8 new NGK iridium plugs and swapped them out the next day, and also swapped the 5th and 3rd ignition coils (just to rule that out). The truck ran fine the next few days and then started shaking again after about 1/2 a mile of driving in the winding Mountain Roads here in Colorado. I pulled over, popped the hood and looked around. When I restarted it it no longer had a check engine light flashing. I carefully drove it to my mechanic, they scanned it and showed it was the same code. I brought it to them about a week later when it started shaking once again and throwing the check engine light, they hooked it up while it was still shaking and we could clearly see the fifth cylinder was in fact misfiring on the live data readout. Of course, then it quit doing it once we tried to drive it. I brought it back to them again a few days later when it started having the same issue, this time the mechanic listened with the stethoscope and heard that the fifth cylinder fuel injector was not making the correct sound, so they replaced the injector with a new Denso one. It ran fine for another 3 days and threw the same code again. I brought it back to them and they tried for three days to diagnose it, and were actually able to replicate the issue a couple times. They also drained the oil and filled it back up with 0-20 full synthetic again and put some seafoam in it. When the mechanic started it up it misfired right away, but then he was not able to get it to misfire afterwards. The next day I even replaced the ignition coil connector plug with a brand new one. It ran fine for another 2 days, and then this morning AGAIN popped the P0305 code after about 1/2 a mile of driving from my house. Sorry to be so long-winded, but I have spoken to several mechanics and even a Toyota service technician, and they are all stumped. At this point I am thinking it might be something to do with an intermittently loose connection where the ignition coil wires or possibly the fuel injector wires attach to the ECM. I am hoping somebody has seen a similar issue and can shed some light for me! Thanks

 

Try asking this guy. https://www.tundras.com/threads/ask-the-toyota-mechanic.2404/

 

Did the problem ever get fixed ?
I’m having the exact same problem, same everything

 

You ever figure this out mtrax?

 

Likewise, going through the same situation, trucks misfiring on cyl 5, replaced spark plugs, coils, and fuel injectors. Was running fine for about half a day before it started misfiring and shaking again, the only thing I could think of right now is it having something to do with the K&N Intake I recently put on but it’s only misfiring on cylinder 5, I think if it’s the intake it would be more than just 5. I’m not sure I’m stumped

 

See my post on it for what my fix was. Valve spring was broken and I replaced it without removing the cams.

 

I noticed some people were talking about a bit of a decrease in compression, I did a compression test on mine and all 8 cylinders ran fine, could it still be the valve spring if the compression is fine?

 

My compression on it was within 10% of others

 

The valve can close but not fully open which is why it misfires

 

Okay cool I’m gonna check it out when I get the chance thank you so much I’m hoping you just saved me a lot of time and sweat

 

Goodluck

 

it was in fact the valve spring, currently in the process of deciding whether or not it’ll be worth tearing the engine apart or not, if so I might as well rebore the cylinders and go up to a 5.9L LOL

 

Sorry to hear it. I was able to replace my valve spring without taking anything more apart. Using a vice, zip ties and a heat gun. I think it’s documented on my profile somewhere

 

Yeah I talked to a friend of mine who knows substantially more about taking apart and reassembling engines than I and he thinks he can do it as minimally invasive as possible so I’m going to try that route, I’ll let you know if we get it worked out. Thanks a lot for the help

 

Same issue, cylinder 5 misfire. Blown head gasket. Could see the leak with a tiny camera. 8K to repair. ouch.