Gen 1 V8 Misfire P0300, P0306, 7 and 8

Hey, Everyone.

Having a difficult time figuring out some misfires on my 2006 Tundra 4.7 V8 160k miles. I hope someone can help me out.

A little bit of back story, I had a coolant leak due to a bad o-ring on the bypass pipe (behind the water pump). Cause a crazy coolant leak. The truck ran great before the leak and during the leak.

I Fixed that leak put everything back together and the truck drove great for 2 days. Then I was hit with misfires in 6,7 and 8

I disassembled everything again and had the fuel injectors professionally cleaned. I also installed all new spark plugs and Ignition coils.

Some coils had cracks others seen better days. Replacing them all just feel like the right thing to do.

I thought that would fix the problem but nothing has changed. Same codes, keep coming back (misfire in P0300, P0306,7 and 8 and sometime before I changed the coils P0302). Truck runs rough, light white smoke out the tail pipe (smells like sulfur).

I am going to go to a local mechanic on Monday. I have a feeling it’s bad fuel pressure.

 

Any chance your timing is off?

 

OEM equivalent parts? (Denso, Hitachi, aisin, etc.)


My pops bought a set of four injectors for his Nissan frontier for the price of one OEM equivalent injector.

Two of the four were "okay." The other two caused serious misfires. (Personally, I've never seen an in-line four cylinder vibrate so much.)

Engine components are worth the extra money for OEM, or equivalent.

https://densoautoparts.com/find-my-part

I recall PHM mentioning that the MAF is Hitachi brand.

 

I will be peeling the timing cover back and checking timing in the morning. I have a new water pump and timing belt kit from Aisin ready to go if that is the issue.

And yes all parts I have put in are OEM or equivalent. The fuel injectors are all Denso and have all new guts when they were cleaned and tested by RCI in Torrance, Ca

 

I doubt its the coil packs or the spark plugs. Would be pretty remarkable if 4 failed at once.

I don't think bad fuel pressure would sneak up like that unless something happened to your fuel pressure regulator, but then I would expect all cylinders to misfire.

Maybe bad timing tensioner and the belt skipped? Did you pull the belt to get to the bypass?

 

Swap coils for 6,7,8 for 1,2,3, clear codes and see if the misfire follows the coils.

 

I put all new coils and plugs in and same misfires happen. I have cleared codes multiple times. I think it’s timing belt

 

I think you are right, I will know tomorrow morning. Heavy downpour today so I can not work on the truck.

I went thru the top of the manifold for the bypass. I should have gone thru the front and done the belt and water pump. Oh well, Expensive life lessons.

Been doing all the work with my pops so it’s bonding time. Beats sitting in front of a tv and now we can can pull the manifold out in under 15 minutes now .

 

Last time I had that happen it was water in the gas tank. Used Heet and drove it 5 miles for it to clear up.

 

This.

 

Is Heet a chemical or a misspelling?

 

Thanks. This is what popped in my head first
https://www.youtube.com/watch?v=uKWgYKa2Fh0

 

Totally understandable. Heet is a popular commodity in my neck of the woods. I always have a few bottles on the shelf.

 

Is it colder, snow bound areas that have more issues with water in the gas?
I don’t hear to much of that in the southwest, unless you go to Mexico and they do it on purpose

 

Or a vindictive neighbor who thinks you’ve parked in their spot. The scratch marks around the locked gas tank door and later a copy of my key I never made sitting in my glove box were somewhat of a give away.

 

Interesting......

 

Water can get into the gas tank any number of ways, yeah, and it's often overlooked.

 

Well I have an update on my issue and I feel like a complete idiot. While I was removing the head originally to do the repair I found 3 random bolts (that didn’t below to the truck) sitting on the manifold. All ready to fall in. Didn’t think anything of it and I have no clue how they got there. Maybe I pick them up on the freeway.

Turns out I missed one and it fell into #7 while I pulled off the intake manifold.

I did put shop towels to cover each hole and I a mirror, magnet and even took a shop vac to each before closing everything up.
And I still missed it.

Even with a flashlight it was hard to see because it was on the inside corner of #7.




The nut is now out, I turned the engine Manually and I have good compression. Looks like the nut wedged itself cause it was very difficult to remove. Will be putting everything back on Tuesday, I hope no damage was done.

 

Good Eye on that.

I had a Banjo Washer fall into and land perfectly inside one of my Infector Holes when removing/upgrading to 12 Holes. I knew about these Banjo Washers being tricky, but this one fell without me seeing where. Started into a FULL @Pucks18 Panic Attack searching all over.

Summonsed up The Spirit of Chief Eagle Eye in the Sky through Deep Breath Meditations and He guided me to Injector Hole #1. It was laying flat in there. Chances? Higher than becoming a Hand Model.

 

Do you have a sharper picture? I’d like to put it in the FOD/FOE ( foreign object debris/foreign object elimination) presentation I have at work. J/K

Although not nearly as bad as the guy who left a peanut butter sandwich stuck to the inside of a missile radome.

Great find! Hopefully no further issues or any permanent damage as a result.