Car knocking, changed spark plugs, problem persists

So I replaced the ignition coils and - voila - problem solved. I've never heard my engine start up and idle so smoothly. After months of dreading a head gasket repair, this has made my year. Fingers crossed that it'll keep running smoothly. Also, today I replaced the water pump and thermostat. Unfortunately, I forgot to replace the coolant temperature sensor before filling up with coolant. I'm not getting any codes related to that, so I'm just going to leave it as is for the moment. I've bled air out of the system in maintenance mode, and plan on taking it for a test drive tomorrow.

I also checked my oil catch can after 2 months of being installed, to find it nearly completely full. It was mostly liquid with a small amount of oil on top. The liquid smelt like gasoline, however. After fixing the misfire issue, perhaps this won't persist.

 

@Mendel Leisk, probably about 2,500 miles since I installed the OCC.

@The Critic, well.. still not a single misfire in 3-4 days. My engine is running at about 180-185 Fahrenheit as opposed to 195-198, so I'm happy about that. I'm not sure if I've 'lost' any coolant since the coils & water pump/thermostat replacement. The level did drop a little, the morning after I bled the air from the system, so I'm going to attribute it to that. Seeing as how just one week ago it death rattled any time the ICE came on (red light, stop sign, driveway, etc.), I'm happy with the improvement. All I can say is I hope you're wrong!

 

I'm in North Carolina. Today we had a lovely 102° Fahrenheit/38 Celcius. The misfiring was actually at its worst when we were having 90 degree F weather, though I'm almost certain the warm temps weren't the reason (that was when I swapped the coils around the first time).

 

How often do you have to empty your OCC?

 

I've returned to cylinder misfire hell. As I said a couple posts ago - I replaced the ignition coils, thermostat, and water pump. After that, for almost a month, my misfires had cleared up and my engine was running perfectly. This was an immediate and dramatic fix. However, as of maybe a week ago, my misfires have returned with a vengeance (specifically cylinder 2 - which is the first one that went before as well).

I tried swapping the 2nd cylinder coil with my old ones, one by one (assuming that I had at least one or two of the old batch that were still in tolerable shape). If anything, the problem worsened, so I put the new back in. At this point it feels like my engine could fall apart at any given moment. I'm almost afraid to drive it. I'm going to school and work though, so I have no choice but to drive it.

I would have thought since it cleared up immediately after replacing the coils, that it was them that was causing the problem. Not sure why the problem has returned after 3 weeks... I would revisit the blown head gasket theory, but I haven't lost much coolant out of the reservoir - not noticeably anyway. The oil catch can did contain *some* oily water, up to about 1/10 of the container, after about 2 weeks - not really a whole lot.. I have no idea what to expect from the OCC, so I'm not sure if that's normal or not. If it were the head gasket, wouldn't it evaporate out of the exhaust?

At this point I don't know what to do other than just replace the head gasket and hope it fixes the problem...

 

Worst case scenario occurred the other day. I got in the car and the engine refused to start. Master warning light came on, along with a "Hybrid system malfunction. Stop car" (paraphrased) warning message. I had it towed to the Toyota dealership and they've taken a look at it and they said the blown headgasket has allowed coolant into the engine for so long that it has reached the "little block" (whatever that means - this message was relayed to me from the receptionist from the service technician). Essentially, the service tech is saying that the entire engine needs to be swapped. I've yet to be given an estimate, so I'm not sure exactly what I'll do. What would be a reasonable estimate to expect and is it even worth it or should I just trade it in?

It's a 2012 with 174k-ish miles. I've only driven it for about 35k miles/3 years and payed about $7k for it originally. This is not exactly what I was hoping for out of a Prius. I really have no intention of buying another 3rd Gen, and honestly may not buy another Prius until the 4th Gens become cheaper. 3rd gens are shit. I really should have had it fixed before now though. It's had a blown head gasket since February. I planned on doing it myself because I didn't have the money to have it fixed by someone else. But the love of my life died 4 months ago and honestly I stopped giving a shit. Between being a full-time student and working two part-time jobs, I just couldn't find the time to do it.

 

After giving it some thought, I think I'm going to look into buying a 2nd Gen Prius for about $5k-$6k. They seem to have far less problems than the 3rd Gen. Only consideration I can think of is the aging hybrid battery. I would look at a Corolla but I've grown too accustom to the hatchback, and camping on a fold-out mattress when I travel. Hybrids (and specifically Prius') are just too damn convenient for that.

In the meantime, I'm going to look into buying a shop crane and swapping the engine on the 3rd Gen Prius myself and then selling the car. That seems like the most cost effective way of getting myself out of this mess. Hopefully within the next few years, as you say, the 4th Gens will be cheaper and I can trade in the 2nd Gen for that.

I guess this entire post will be a warning to anyone who considers buying a 3rd Gen. Buy at your own risk. .. My parents also own a 3rd Gen and have started having early signs of the death rattle within the last few months.

 

I've driven it with a blown head gasket for around 9 months now, with a constant coolant leak. The service tech at Toyota claimed that simply replacing a head gasket wouldn't be enough to salvage the engine. I have no way of verifying if he's telling the truth, but from what I've heard of head gasket failures, I can believe it for 9 months of driving it like that. I guess I could have it towed elsewhere for a second biased opinion, but I'm not sure I would be better off. I would open it up and take a look myself, but rebuilding an engine (if it's worse off than just the head gasket) seems to be a much more daunting task than simply swapping the engine, for someone on the DIY level like myself.

However, after mulling it over, I might just keep the car after all. I'm looking into buying a 4th Gen engine with low miles to swap with the current engine. Replacing the head gasket on the current engine would seem like the simpler and cheaper thing to do, but from everything I've read about 3rd Gen engines, I'm not sure I want to risk dealing with them anymore. If it's as the service tech says, I may be simply postponing my mechanical troubles. That's a lot of time off from studies to just push doomsday back to another month. I'm not sure. I'm always open to suggestions.