Hi everyone, I have a 2014 Prius Plug-in with 159k miles on it. It's been a great car, but recently, it was running a little rough for about 10 seconds shortly after I began driving, when the engine was cold. It only lasted 10 seconds, then went away. This happened 2 or 3 times, then after the third time the check engine light came on. I got code P0302. Oh no. So I got a combustion gas tester, used it on the fill tank, and the fluid stayed blue. But I was wondering how effective it would be on the fill tank, because it's supposed to be used on the radiator cap, but as far as I can tell, the Prius doesn't have one. Next I pulled the plugs, and did the water test, holding paper over the spark plug holes while I briefly ran the engine. No water on the paper. The ceramic on the #2 plug was not white, it was brown just like the other plugs. So I bought a new set of NGK iridium plugs, installed them, switched the #1 and #2 coil, and test drove it. No shudder, no check engine light. For a few days. Today the shudder happened again, and I got a permanent code P0302, along with pending codes P0300, P0303, P0304. I'm guessing that I have a crack in my head gasket, but why did it pass the paper test? I keep hoping it's something else, but in the back of my mind I'm pretty sure it's the gasket, since it's such a common problem with this car. Should I start shopping for a head gasket repair, or a replacement engine? The car is otherwise in decent condition, seems like it should have a lot of life left in it, and I'd like to keep it for a while longer. Thanks in advance for any advice. -Tim
I don't know who came up with that "paper test", because it's invalid! We are talking about vaporized droplets of coolants, not water squirting into your combustion chamber. You stated that the misfire happens when the engine is cold, then disappears. When the engine heats up the metal engine expands and seals the head gasket leak. You can verify this by sticking a borescope camera down the spark plug holes. The top of all pistons should be universally pitch black with carbon; if they aren't - they're being steam cleaned by the small amount of coolant seeping in and combusting. Your getting multiple pending misfire codes, because your ECU can't figure out which cylinder(s) are misfiring - because it's occurring intermittently. Start pricing a head gasket replacement and EGR clean out. The sooner you get this done, the better your chances that the repair will last a long time. The longer you run the car like this, the higher your chances of bending, breaking, and/or cause a head gasket replacement not to last too long. Hope this helps......
OK, thanks. That is very helpful, and confirms what I suspected. I saw the paper test done by a mechanic on youtube, but I don't remember who he was. We stopped driving the car, I'll make some calls on Monday. I see you're not too far away in California. Do you happen to know what a reasonable price is for this job?
Sorry, don't know of any quality shops that I would trust. I've heard good things about Gasket Masters that specialized in this kind of work and can get it done in a day. Check the locations' yelp reviews before committing. Toyota Prius Repair Shop Manteca, CA | Gasket Masters Inc Good Luck...
