I broke down 3 miles from home :(

Hi guys,

My beloved 2010 Prius III gave up last night. I was about 3 miles from home leaving a parking lot. Started with electric and then the ICE kicked in. Nothing extraordinary at first but a few hundred yards later when I stepped on the gas, I heard some weird noise and lack of power from the gas engine. I let go of the gas and the noise went away. The ICE was still running but kind of idling. I stepped on the gas again and the same happened. This time I pushed it a bit more and started hearing the unmistakable sound of knocking.
It was worse when you push the pedal more. I wanted to see if I could make it home. I found a sweet spot where the knock was barely audible and the car was moving at a very low speed (around 30mph). Drove about a mile in this state using the HV battery as much as possible. Stopped at the light; ICE off and 5 bars on the HV battery. I was about 2 miles away. Light turned green, and I started moving (battery at first). Then the ICE kicked in. Same issue and it felt it was getting worse. Pulled into a gas station a few hundred yards later. Popped the hood to see if anything looking unusual. I checked the coolant level and it seemed okay. I couldn't see anything obvious. I decided to continue. Left the gas station on battery (still around 5 bars). If it was a few years ago, I could have made it home from that point on EV mode slowly. But my HV battery is very week now. I can't even get a mile out of it. Anyways, I am on the main road again on battery power but then I had to kick the ICE as the battery dropped to 3 bars. Right at that moment, the CEL finally lights up on the dash. Engine started knocking as soon as it fired up and knocking continued. I kept driving at below 30 mph this time with the hazard lights on. The car had no power at all, the engine knocking terribly and getting worse, and I only had about a mile left to arrive home. If it was someone, I would probably recommend not driving it anymore but as I thought about the steps involved to get this car towed to my home, I took the risk and all the responsibility and decided to get there. Soon, I got off the main road and with just a little over half a mile left. I was driving in the neighborhood roads; I was driving as efficiently as possible. I had to run a few stop signs. Not proud of it but I couldn't afford to stop. Luckily roads were pretty empty (around 10:00pm) I was moving barely at 20 mph so it was very easy to stop if needed.
In the last few hundred yards, knocking got so bad and my battery is at 2 bars. So, no way of shutting down the ICE. I arrived with the ICE running the HV battery at 3 bars; I parked the car on the street and shut it off. Popped the hood again and when I leaned down, I got some burning smell. Not very strong but it was there. The engine wasn't hot. The burning smell went away quickly.
I got my scanner and read the only trouble code P0302 (Cylinder 2 Misfire Detected). It was very obvious that it was a misfire but I was surprised to see only one cylinder. It felt like there was only one firing out of the four. Freeze frame data showed the coolant temp at 181F when the code was set. I know the engine didn't overheat and I don't think this is simply a defective coil or injector (I wish it was). I am thinking I blew the head gasket.

BTW, it is at 199k miles.

I am going on a trip in 2 days. I won't have much time to spend on it, but I have to have a plan for my return. Luckily, I have a backup ride and won't be grounded. But I will be missing my 60+ mpg ride a lot.

So, let me know what you guys think.

 

Well, I heard a cat theft became pretty common but do you really think that someone will steal it in a Home Depot parking lot in 15 minutes?
It is not impossible for sure but if so, the car would scream but the engine wouldn't miss. It would probably be crazy loud.

 

I replaced all 4 plugs in 2018. They have about 50k miles on them. If it turns out to be spark plugs, I would be stunned but at the same time very happy.

 

Thanks man, I will perform some diagnostic checks today/tomorrow for sure. This turning out to be an ignition system related issue would be like a Xmas gift.
She sounded bad last night. Hoping there wouldn't be a mechanical damage.

 

I got them from an ebay seller back in 2019; he had a good rating. They came in an OEM packaging and looked original Denso plugs. But that definitely is not a proof that they couldn't have been counterfeit.

I will pull the Cylinder #2 and check.

I had a plug went bad on me before on a 4-cylinder Ford. It was missing but was still drivable and wasn't knocking at all. When I pulled the plug, I saw a crack on the ceramic body.
I had an ignition coil went bad on me on a 6-cylinder BMW and it was missing for sure but still perfectly drivable and wasn't screaming.

Still hoping for the best but getting ready for the worst.

 

Well, I was definitely hoping to roll the 200k without a major incident. I was very close. Dang it.
But I will do my best to bring her back on the road.

 

Hi guys, thanks for all the comments. I thought I would at least pull and show you that plug but couldn't do it today. I was very busy all day getting ready to leave town for several weeks. But I will do that tomorrow and post a picture.
I need to get this car back in garage. It is currently on the street. Today, I was thinking how to do this without running that engine again. I am low on HV battery, it won't let me pick "EV" mode. But then I remembered I discovered a way to not let the ICE come on. When the car is in neutral, it won't start the engine till you put it into the gear no matter what the state of charge is on the HV pack. I think it is because it knows that it won't be able to charge the HV pack in "N" mode. Simply there is no reason to waste fuel. I will do this to get the car into the garage tomorrow. Then pull the #2 plug out.