Just Purchased Used 2012 G3 Model 4 - Need Advice

As the title says, I just bought a used 2012 Gen3 Model 4 last Friday. It had about 170K miles on it, which, I thought, it being a Toyota, would be OK. The CARFAX showed all the maintenance had been done on the car for the life of the vehicle and it was services at regular intervals by a Toyota dealer so I didn't get a 3rd-party opinion at a shop.

Monday morning was colder than it has been and when I started it (I live in Utah, it dipped to 46 F overnight, not that cold, but colder than it had been), I experienced a rough engine start and thought the engine was going to fly apart. I freaked out and shut off the engine. When I started it again, it had gone away but the check-engine light was on. I took it to a shop who was able to read codes P0300, P0301, and P0302 - Cylinder Misfire. I later found this forum and this thread discussing the exact issue - Rough engine start | PriusChat. The same thing happened again this morning and I was able to get a short video.

I took it to a mechanic today to have it looked over. He would have like to keep it longer for a more thorough diagnostic, but I mentioned the few threads I found here, like this one - Oil Catch Can, Eliminate that knock! | PriusChat - discussing using an OCC to eliminate the engine knock. With the car started and the ICE running, he took off the oil cap and felt the air pumping out of the top of the engine and had me do the same. It was A LOT of air, which he noted was because of the blowby (as discussed in the thread by danlatu). He also mentioned it could be the spark plugs or timing belt/chain need replacing.

Here's my question: How concerned should I be? In my zeal to purchase a car for what I thought was a good price, did I screw up and get one that was worn out? Do I need to have the engine rebuilt and new piston rings installed?

I'm not looking forward to A) Pumping a lot of money into a car I just bought and, more importantly, B) Telling my wife I messed up by not having a 3rd-party mechanic look at it.

 

As a small update, I've continued to have issues with the violent engine shaking at other times of the day, not just first start in the morning. Today, for example, I drove the car about 20 minutes, parked for about an hour, then drove it again and had the shakes. The same thing occurred this afternoon under similar circumstances. I'm really starting to worry that I might blow a head gasket, or something.

 

Ok, but what's the fix for this? Clean the intake plenum (remove all floating oil/water/fuel) and get an oil catch can?

 

As a long overdue update to my issue, it did turn out to be the head gasket. The knock continued to worsen right up until I took it in to replace the Intake Manifold, spark plugs, PCV valve, and have the EGR system cleaned out. I was leaking coolant and had to add about 2-4 cups a day (my guess, I have no idea how many cups it holds). I asked the shop to take a look and they did a pressure check and were able to see the coolant leak.

It turns out after putting the VIN into the Toyota owner's page, a customer reported the exact knocking issue with the same recommended diagnostic procedure - coolant pressure check with camera. This issue was reported to Toyota only 124 miles before I bought the car and sadly wasn't on the CARFAX report. I called up the dealer and sent over an email with a report on all my research here on PriusChat and the work I had done on the car. They agreed to replace the engine if I bought an extended warranty. Thankfully it's half the price of a new engine install (I know some could do it for cheaper, but I don't have access to the resources to do it myself). Still waiting on the repair and have a loaner car in the meantime. I plan to put in an OCC once I get the car back. Hopefully with the newer engine and considering all the new parts and cleaned out EGR, this will keep things running smoothly for a long time.

 

I looked into this and it has more to do with it having a Branded title, which I'm fairly sure this wouldn't be. There may be something else my situation may qualify for, so I'll have to look into that. Thanks for the idea, @grid.