Engine Code P0304 - Cylinder 4 Misfire

It has been a while since I have posted anything but I thought I would share my recent maintenance experience.

I have a 2005 Prerunner with the 4.0 1GR-FE 6 cylinder engine and it currently has about 143,000 miles

On Sept 15 my check engine light (CEL) came on after I noticed rough idle at start up when the revs are coming down after the initial high rev you get when you start the truck. The truck would run fine and idle fine after that, it was just the initial start up I noticed the rough idle.

I got the code read at Auto Zone which came up a P0304 Cylinder 4 Misfire. I took it to the dealer on Sept 17, they got the same code and indicated it was a bad coil on cylinder 4 and replaced it and all 6 spark plugs.

Then a few days later on Sept 20 the CEL came back on. So I went back to the dealer, this time they replaced the fuel injector in cylinder 4.

Then a few more days went by and on Sept 25 the CEL came back on and this time they decided it was the head gasket that was letting coolant into the cylinder.

I just picked it back up today and everything seems to be running fine so far. I talked to the tech who performed the repair. He said that under pressure using the scope he could see coolant coming into the cylinder. The leak was so small that you can't even see anything wrong on the old gasket. I didn't notice any loss of coolant and I was not getting any white smoke out of the tail pipe.

The tech also told me that he removed the engine to perform the repair. I had them replace both head gaskets since he was already elbow deep in the motor.

On the positive side of things he said the engine looked real clean. There was no sludge or residue in the oil pan or any metal shavings.

After all was said and done I am into this thing for agout $2,700. I was a difficult decision the have the repair done but since the truck is paid for and I plan on putting another 100,000+ miles on it I thought it to be a good investment.

Hope this helps someone else in the future.

 

I've been having the exact same problem. 2005 Tacoma, v6, 4x4, dbl cab, no modifications (yet!). Rough start up, calms down after a few seconds, and throws the P0304 code. I've been in and out of the dealership since Aug 17th with this problem. Initially they said it was the V/C gaskets, $580 changed both those out and still had the problem a few weeks later. Now after 4 more visits, they have checked "everything" they can, it must be a cracked cylinder head or block, and it's cheaper to just a get a new engine. (I've also posted a separate thread about my issue).

I'm at the point now of going to other multiple shops, see what they say. But from my research on here and other forums, it seems to be a common problem, with several postings a month about it.

Did the dealer do a compression test or leak down test? Did all other testing come out ok? Did the tech say anything about what led him to the head gasket?

Hows it running now? Did the HG fix do the trick for good?

 

things like this make me very nervous. thanks for posting as im sure this info will be invaluable soon. now we just need a good head removal rightup lol

 

I have an 05 prerunner 160k miles And I'm having same problem. Rough startup and miss fire p0300, p0304, p0302. The problem disappear a few days and then come back.
My dad has and 05 and had the same problem, his problem was a burn spot in cilinder head gasket and and stick valve.

 

I recently got code P0304 on my 1996 V6 Tacoma, 115K miles. My truck had been experiencing rough idle and some hesitation for a couple of weeks. While on the highway it got a lot worse, and the check engine light came on. Took it to the dealer, they replaced the #4 fuel injector and the spark plug wires. Also replaced the valve cover gaskets, which had a small leak and needed to be replaced. Total bill $1180 including tax. It is running great now.

 

To save money I would try to change coil packs and spark plugs first since those are maintenance items that need replacement anyways. Here is a video I followed to change them. I had been lurking on the forums for a while to get a fix. I was fortunate enough that it was only my coil pack causing the issue and not something bigger like some of you guys. Here is a link to the video https://www.youtube.com/watch?v=_7jC8yKh2D8&t=25s