2011 Prius P0303 misfire

So far so good! Wife even said it hasn't driven this good since we've had the car. Fingers crossed from here on out!

 

It's been a little over 2 weeks of very heavy driving (over 1k miles) and still good. I'll call this issue fixed! It's driving better than it ever has since we've had it. All in all this was not too difficult of a job, just time consuming (took me about 3 1/2 hours of really taking my time). If you can replace the spark plugs in this car and clean out the egr pipe you are already pretty much there anyways. I cross threaded one of the fuel rail mounting bolts. The other is just fine and holds tension without issue. I'm going to use the red hi temp thread locker (this stuff

not the red high strength one) on the good bolt so it'll stay in place permanently. Right now it's holding tension without issue but we have a 500 mile mountain trip coming up next weekend and I see this as cheap insurance. Once it cools off outside in the fall I'll look at getting a thread repair kit for the stripped bolt/hole so we have a permanent fix. No I have not changed the coolant yet. I'll have to look at the mileage but it's roughly around 160k. From what the carfax shows this was kept up at the dealer. Every fluid I've looked at so far looked brand spanking new.

 

Scratch the hi temp thread locker idea. I'm back to the drawing board and will be fixing this weekend.

 

And we got almost 5000 miles this time. P0303 is back...Going to pull the plug tonight and look to see if it's fouled. UGHHHHH

 

Just checked the oil and bone dry at 5k miles. We used bulk 0w20 this time. I added a quart of 0w20 I had laying around and that didn't even put a dent in this. Going to try changing the oil with mobil 1 high mileage 0w20 and run some gumout through this. The engine got hot and probably coked up the plug I'm thinking.

 

I pulled the plug and it looks nasty! I looked at the other plugs and they looked normal. Now the oil had maybe 3 quarts in there. Did a drain and filled it up with mobil1 HM. Used the cheapo fram filter at Walmart. Going to keep an eye on the oil level and color and may just do a few short oci's to clean things up in there. If I had to guess maybe there is a bad seal allowing oil to creep up to the bottom of the plug in the 3rd cylinder?

 

Nutz the top half was dry and this only seemed to affect the electrode area of the plug. Would that point more to the valve stem seals?

 

No coolant is being consumed. I'll check the throttle body this weekend. If it is indeed the valve stem seals that's out of my comfort zone and a job for the mechanic. The valve cover and spark plug tube gaskets I could do though

 

Not sure how to edit. No oil light came on

 

We are on mechanic number 3. The 2nd one kept the car for over two weeks and nada. We are picking up the car from this mechanic and taking it to one that has very good reviews. The 2nd was the family mechanic and looks like they just have more work than they can handle right now. That and seems like as soon as the word hybrid is mentioned around here the mechanics lock up. I'll keep everyone in the loop on this one and HOPEFULLY we at least will have a diagnosis this week.