2014: probable HG fail but let me know what you think

Started getting rough starts on my 2014 Prius, 163K miles. Kinda rumbly/vibration that would clear up usually in 10 seconds or so. Usually on start only (or first IC kick-in if car was warmed up and started in EV). It's teasing me...like I started it the other day and it was fine, did a 2-hour drive, heavy traffic, start/stop IC constantly - all without apparent issues until right before I parked and it did a rough IC start-up. I'm sufficiently pessimistic about it to have bought a 2nd used Toyota (non-Prius) this past weekend since we're moving out of the city and need reliability. Details:

• My coolant/oil levels seem to be unchanging, or not dramatically changing b/c I don't see a drop.
• There isn't much smoke out the tailpipe, you really have to look to see anything presently (very faint puffs, assume condensate or coolant burning off)
• Besides worryingly consistent rough starts, the situation is kinda the same as this previous post from last year.
• Misc and specific (1/2/3) misfire codes (from memory, 300, 301, 302, maybe 303?) and check engine light. Cleared and it'll stay clear for a few drives then come back. The situation is pretty new.

I'm wondering what my options are? It's not worth having a mechanic/stealership fix, it'll be too expensive and it's also needed a battery (P0A80, I carry an Android phone with Torque Lite to reset it every week...)

• I know the answer is I shouldn't drive it, but does the unchanging coolant and oil levels mean I'm safer than if it were hemorrhaging coolant? It would be nice to be able to drive it upstate where I have a garage where I could park it and maybe DIY a HG repair.
• Is it worth taking it to a mechanic for a leakdown test or at this point can I safely assume HG is failed and not waste my money?
• Sell it with all disclosed as a mechanic's special before it totally dies?

It's a real shame...Prius 5, love it, only have had it 1.5 years and put some money into it too...damn.

 

Wondered about the plugs and not sure last time they were changed! I'll look into that, though I do think these aren't originals. I have a vague memory of plugs in the service records but will check and report back. (EDIT: see next post, yes they were changed)

Thank you and keep replies coming. I am particularly interested in what to monitor in this situation...even with bad HG, if coolant level is stable, is it less risky (still bad I'm sure) to drive it a bit longer than if fluid level was changing? I feel like risk of overheating is reduced at least and it becomes an efficiency and power problem (until it gets worse).

 

Sadly replaced at 127k. 37k or so ago.

 

How long did you drive it in that condition? Yes, I'm in the "bargaining" stage of grief...

 

Dealer service at that mileage. Part number 9091901275 x 4.

 

I don't see it in the svc records and I have not, living in the city and not having a great place to work on the car for any long period of time. That's why I'm hoping Prius will behave/survive long enough to go 2.5 hours to the garage upstate where I can settle in and work on it if I don't just sell it. I've been watching videos and it's all a bit intimidating (although Mendel I literally just heard a shout-out to you in Merv's intake manifold cleaning one!)

 

You have correctly intuited my state of mind for any pending trips, McCoalroller. Indeed this situation has even forced me back into deadly NYC traffic on my bike (no mean feat at my age) instead of squandering precious engine hours commuting to work while we wait for the check to clear/get title on keys on the other used Toyota. A/C tip is a good one.

Thanks everyone for the help so far.