Misfiring mystery

See Tech is stumped. What causes this misfire? | Page 3 | PriusChat

This was my experience exactly, and it turned out to be a rotten fuel filler neck that was allowing rain water thrown off the rear wheel to contaminate the fuel tank.

 

Anyone know what the fix was to this issue? I have a seemilgly bad cylinder in a 2008 with 180k miles. Getting a P0301 and a flashing CEL. I’ve swapped every sensor that is related to ignition or fuel. I haven’t checked the fuel pressure yet. Suspecting a bad valve or rings.

 

Kstoner, this thread is going on 4 years old, and if all you have is a single cylinder misfire, then there isn't a "this issue" as if you have the same one. In addition, this is the Gen 1 forum, while you have a Gen 2.

You should start your own thread in the Gen 2 forum and provide as much detail as you can - stuff like mileage, maintenance history, etc.

Note that the P30xx codes are called "misfire" but should be named "miscombustion." They are just sent when the a/f mixture doesn't explode. This basically happens for 4 reasons: no spark, fuel amount is off (none, too little, or too much), air amount is off (too little / too much), not enough compression. I don't know what "swapped every sensor that is related to ignition or fuel" means, but often the best thing to start with for any single cylinder misfire code is a compression check. That will tell you about rings and valves.

 

So far, I think you've been their MO. Look in the valley around your injectors for gas. It's easy to not get the injectors in correctly and cause a leaky o-ring, which would give you the gas smell. Take off the air cleaner to see in there.