I have an '04 SR5 V6 with 105,000 on it. Recently it started misfiring for a few seconds at startup. After 15-30 seconds the engine would run fine. The CEL came on. I pulled the code, P0306 Misfire on cylinder 6.

I changed the plugs, since they were due for replacement. The plug on #6 was covered in oil. Obviously not firing. I swapped the #4 and #6 coils around to eliminate the possibility of a bad coil.

I started it up and I still have the same issue. Misfires for 15-30 seconds then runs fine, CEL and P0306 code.

What concerns me is the oil on plug I pulled. I'm worried it might be a bad valve. However, I haven't been using any oil. I've run Mobil1 since I've owned the truck and it's always had regular changes.

I've put 70,000 on this truck in 2 years, it's been run pretty hard. At the same time, I've never heard of any valve issues with these engines.

I did a little searching and found a few other people with the same issue on the same cylinder, but no resolution. Any other thoughts or ideas are appreciated.

 

If there is oil on the tip of the plug, you have valve guide/valve guide seal, and/or oil control ring issues.

Do a compression test dry, then do one wet(couple squirts of oil in the cylinder. Keep the throttle wide open, pull the fuel pump relay also while doing this.

If compression increases (> 10%) during the wet process, you have bad rings. If not, it points to the guide seals.

 

Just incase anyone is searching....

This ended up being a cracked head/blown head gasket. From what I've researched, fairly common on high mile 4.0's

The engine has to come out on the 4Runner to replace the head/head gasket.

I traded it in on a new Tundra

 

Thanks for the heads up. I wasn't aware this was a common problem with our engines.