The dreaded P0304

Not too long ago I the check engine light turned on in my dash on my 05 taco dclb. Four days went by and the light went away. Sweet! Looks like I don't have to do anything. I couple weeks go by and the light comes on again. Damn! Looks like I need to do something about it. The BAM it goes away again. At that point I realized I need to get off my lazy butt and look into it. I found a friend that has a OBD reader. I took it to him and that's what gave me the code P0304.

I took it to google and google never lets you down! No matter what symptoms you google whether for you or your vehicle, BAM you're sentenced to death! LOL. Google had me thinking that I was about to be anywhere from $2000-$4000 lighter depending on where I got the work done. The internet told me I needed a new head gasket or even a new head... We all know everything you read on the internet is true!

I started off by changing the plugs and BAM the light went away and everything was right in the world again. Until it wasn't LOL. Light came back. Checked it again and it was the same code. It just so happened that it was now my turn to get my TSB leaf springs. I took it to the dealership to get that done and while I was there I had them diagnose the problem. They quoted me $90 for the diagnosis. I figured $90 was a fair price for a piece of mind because I didn't feel like chasing the problem changing every little thing one at a time until I changed the right piece. They said they did all kinds of tests and that the only problem they could find was a bad coil pack. They then quoted me almost $300 for a new coil pack. I said thank you but no thank you.

I went home and ordered a DENSO coil pack from Rock Auto. They had the best price around. I installed the new coil pack and she has been puring like a kitty ever since. I even marked my radiator overflow just to make sure that I'm not leaking small amounts at a time. So far my fluid level has not moved at all!!! I'm even getting roughly 20 miles more per tank fill up!

I haven't read any happy ending stories about the p0304, or any cylinder misfire code at all. I figured I would write up my feel good story. At least it made me feel good

I believe I spent under $200 with the new plugs, dealership diagnosis, and one new coil pack

 

thanks for the write up, my 2.7 recently threw the same code and it also went away but i expect the problem to return. Ill be looking into the coil packs. Mine has 206k on it, may be time to change it out anyways

 

I'm not reading any drama, or complaints, or searchable questions....WHAT AM I SUPPOSED TO DO WITH THIS


kidding, congrats man...always nice to read a 'win' story Glad it was a relatively cheap and easy fix!

 

@rjbiii
Don't forget to change out the plugs while you're at it.

@eon_blue
You want some complaints? I have plenty of those! When I took my truck to the dealership for the airbag spiral cable recall, they left my steering wheel crooked. When I called to tell them about it the lady on the phone said my alignment was off and that is was X amount to fix it. I tolled her "then why does my truck still stay in the lane when I take my hands off the steering wheel?" she couldn't answer that but still said it was my alignment. I fixed it myself and it took less time than the conversation I had with the lady on the phone. The removal of the airbag scares the fudge out of me but you can find anything on youtube

Thanks. I was happy about that too! Now I can continue to save for my lift instead of fixing a head gasket.

 

Good call ill definitely change those out while I'm at it, but i don't think its them, since they were changed at about 80k miles ago. Doesn't hurt to eliminate that as a possible problem while I've got it apart though. Thanks for the tip

 

According to what I read on the interwebs, a faulty coil pack can kill a plug. For a few bucks more why risk it.

 

Very good point, definitely worth changing out to avoid problems later on down the road.

 

it should also be noted that if you clean your air box, maf sensor, and throttle body....when you go to start the truck it will throw a cylinder misfire code almost every time. its just the cleaners being sucked into the combustion chambers and being burned off. nothing to worry about. just drive gingerly for a day and clear the code right after it comes up.

 

I've never cleaned any of those but I'll keep it in mind for future reference. Thank you

 

i used the CRC products that i got from walmart. there is a write up on here but its pretty easy. you just remove the entire intake and open the flapper on the throttle body. spray throttle body cleaner in there and use and old tooth brush to clean as much as you can reach. spray a little maf sensor cleaner on the maf (DON"T TOUCH IT, FOLLOW THE DIRECTIONS) and clean your air filter/ air box then resinstall everything. do not start the truck with the intake removed.

 

Thank for the tips. I'll take a look in there. I have an aftermarket airaid intake and I just cleaned and re-oiled the filter last week. I also prefer using CRC products over other brands.

 

If you run an oiled filter, its actually recommended that you clean the throttle body at least once a year or so

 

uh-oh... It's an 05 that my dad bought brand new from the dealer and he installed the intake. I bought it from him a few years ago when he upgraded to a Tundra. It's been cleaned never. Should I clean it 11 times to catch up? LOL J/K

Now I know what I'll be doing tomorrow. The paint is also feeling kind of rough. If the weather holds up then I'm also going to give it some clay bar love

 

Here you go:

https://www.tacomaworld.com/threads/how-to-throttle-body-cleaning-2005-v6.94203/

 

Much appreciated. I was looking for it but you beat me to it.

 

I dug around for it. Followed it myself. Was glad to have it.

 

I'm curious to see what it's going to look like in there. Also, I thought it was running like a champ after I changed my bad coil pack. I couldn't imagine it getting any better. We shall see. I'm excited about this.

 

Looks like my coil pack must have been messed up for a WHILE. For as long as I can remember I've always gotten 250ish miles per full tank of gas. I always pump chevron gas 91 octane. The fill-up right after the new coil pack went 275ish miles. Right now I'm at 285 and counting. I'm thinking I can hit the 300 mark before the gas light turns on.

I wonder how much better it'll get once I clean the mass air flow sensor and the throttle body. I'm starting to feel like I'm getting Prius mileage lol.

 

It pays to have a code reader for sure. I got one for less than $20 off of Amazon and have used it more than once, saving me lots of money. Most recently I got a CEL codes 0455 and 0441 and after looking it up tried the first thing that I could do to fix it - screwing on my gas cap that was just sitting at the top of the threads. Already had called in to work letting them know I wouldn't make it when I had seen the CEL on the way there and enjoyed a nice paid nap that day lol. I guess a reader can help cure sleep debt too lol.

Also, sending an oil sample to Blackstone Labs for $25 will definitely give you a lot of info about what's leaking into your engine. Here's a cool video that goes over the data from a Ford Windstar with 300k miles on it:

 

It turns out that yesterday I had 275 and not the 285 miles on this tank of gas that I thought. Today I made it to work and the light turned on at 290. That's 40 miles more than what I was normally getting before changing the coil pack