2010 P0302 Cyl 2 Misfire & White Smoke

A few days ago I threw P0302. Rough ICE start, but after a few seconds of forward driving everything was fine. CEL went off on its own (this has happened twice).

MPG hasn't dropped (I get 50-51 according to the computer, which is 47-50 in reality). Today I put her in Maintenance Mode and saw white smoke puff out for about 30 seconds, while the rough start commenced. After 30 seconds, no white smoke and engine is normal. I fear this is the early warning of a blown Head Gasket, or worse?

171,000 miles, drives great, 50+mpg, has a new factory hybrid battery which was replaced under warranty in July 2015 at 112k miles. Body in amazing shape. Hoping to not have to scrap her.

 

Update: Today I took the following actions:
(REMOVED WIPER ASSEMBLY)
SWAPPED COIL 2 & 3. BOTH HAD RUST/DUST (SEE PHOTO)
CLEARED CODE 0302, 0302P
STARTED UP - - NO STARTUP HESITATION, KNOCK, OR PING!
DROVE ABOUT 15 MI, DROVE NORMALLY HWY AND CITY
COOLANT LEVEL JUST BELOW "LOW" AFTER 10 MILE DRIVE

NEXT ACTION STEPS:
DRIVE UNTIL CEL COMES BACK. IF NO CODES, PULL ALL SPARK PLUGS (REPLACED 20K AGO). IF NO WATER OR WHITE POWDER (DAMAGE), REPLACE COIL PACK(S), REINSTALL WIPER ASSEMBLY, DONE

OTHER:
CHECK WATER PUMP FOR FLUID/WHITE DEPOSITS
DRIVE FOR A FEW DAYS W/ANTIFREEZE IN TOW
IF P0302 RETURNS, TO MECHANIC FOR COMPRESSION TEST CYL2, DIAGNOSE.
BAD WATER PUMP?
ASK THEM IF THEY RECOMMEND BAR'S HEAD SEAL

 

UPDATE #2

Tonight, about 6-7 hours after my 15-mile drive this afternoon, I cranked her up. Similar sounds to the rough start / misfire I was getting prior to today. No engine codes thrown yet, but I did notice something weird:

Earlier today when about 5 miles from home, I reset my Trip Odometer to run a short-distance MPG test. Now I know the Prius cpu MPG estimate isn't gospel, but when I exited the car this afternoon, the MPG was around 70-75 (over these 5 miles - yes I'm a granny). When I entered the car this evening, the MPG was down to 55-60! I drove 1 mile to the grocery store (mpg held as normal on this trip, even ticking UP 1-2mpg because I'm a granny). When I got back in my car, mpg was down to 47-48! (By the time I got home it was back up to 50.5MPG) Now, this may be because the tank is very low (probably 1/8 full), but is this reason for alarm nonetheless? This afternoon the coolant reservoir was not cloudy. I did not and do not smell gasoline leaking anywhere under the hood, and I'm very nose-sensitive. We'll see.

PS: I've also come to realize the "white smoke" of death I feared in my first post is, I believe, normal exhaust. Even tonight during the rough start / misfiring, I stuck my nose in it and it smelled like normal exhaust.

 

I haven't cleaned the EGR circuit, I've never done that and would have to research how if I did. I've cleaned MAF sensors and throttle bodies before, so that is one of the next steps I'll probably try since they're pretty easy to get to.

I'm monitoring the coolant level. Yesterday it was stable. After driving 7 miles it was at the "low" line. At cold start it is well below the "low" line. I've bought some Zerex Asian and will add it today, as I don't know where to get Toyota Super Long Life coolant on short notice.

I'm in L.A.

 

UPDATE #3

Having sat for a full 24 hours, I cranked her up again tonight for a short drive. No hesitation, no knock or ping or awful clanging of metal (I assume that means no misfire). However, when I shimmied around to her end side to inspect that thar exhaust, I could tell she was choking on something. A quick nose-down to the tailpipe and I instantly smelled through the pipe gasoline --- unburnt gasoline. I know this wasn't from a leak out her back or underneath or under the hood, because I checked all three before cranking up -- no leaks. Coolant level hasn't changed much since I checked her yesterday.

I drove her for only a mile or two tonight, but so far no Codes thrown since I cleared them yesterday.

I've a knowledgable farmer friend (driven tractors his whole life) advising me this is a bad coil (he says fuel can just sit inside a dead cylinder and then get burnt out when you drive or crank). There doesn't seem to be any other reason that an unburnt Gasoline smell would exit her rear end, but I could definitely be wrong. Next step is to keep driving her until CEL comes back on, whilst fastidiously monitoring coolant level -- if CEL indicates the Misfire has moved to Cylinder 3, I'll know it's the coil for sure. Unfortunately our Prii don't give us a temperature reading until it's too late -- unless I'm mistaken.

I did notice oil tonight on the bottom part of the engine. Pretty well caked on there. Probably need a new valve cover gasket (I've had this happen before on a Lexus) and I don't think this is related to my current problem. However, it's not losing much; oil level is normal and it was changed probably 2-3k ago.

 

Poking around the web with "misfire gasoline smell exhaust," I'm starting to believe it may be a clogged fuel injector. I have zero experience with this, however, so I might just take it in

 

Thanks. The dipstick and oil cap look normal, not cloudy, oil is pretty clean (for being 2k-3k old) and level is good.

Coolant levels, I can't say how long it's been at the Low mark since I only started monitoring it a few days ago. Mechanic didn't say anything about it when they changed the oil 2k-3k ago.

Longest trip about 15 miles. A longer trip not a welcome prospect in traffic-choked LA... but I might try later.

 

Thanks! I will see if the CEL comes back and if misfire remains in Cyl 2, may change the injectors.

 

Today completed 83 mile round trip, mostly highway (roughly 40 each way without stopping) after which Prius dash shows 56.7 MPG. Rough/hesitant starts all day, still the raw gas smell from exhaust for the first 20-30 seconds of idle. Intermittently-hesitant ICE kick-ins (the moment the ICE cranks up while driving), though 90% of the "kick-ins" (sorry I don't know the right term) were smooth, and once ICE had finished coughing out whatever was in there (I assume unburnt gasoline), the ICE and Hybrid system sounded and operated normal.

Code P0302 P (Pending) came back after first 40 mile trip, and P0302 & P0302(P) reunited after the full round trip. This tells me the coil that had been on 2nd Cylinder (which I have swapped with the 3rd) is not bad. Maybe spark plug in Cyl 2 (which is still in Cyl 2 - I haven't pulled any plugs yet) is bad, or perhaps fuel injector #2?

Before starting her this AM I topped off the coolant (Zerex Asian, sorry purists) to the "seam" in the reservoir (just above the "Low" line), and after each 40-mile trip today the level had not moved.

 

It'd crossed my mind earlier that it might be the 12v battery. Will investigate.

 

Thanks for this. I haven't pulled the injectors yet and would rather not, though I can. By "double dose of Techron" do you mean pour two bottles in a single tank? Or just treat two tanks in a row?