Cylinders misfiring

is the coolant level okay?

have you cleaned the egr circuit?

there are a lot of fraudulent parts out there.

 

If this started after u replaced the plugs and coils, its probably the plugs and coils. I would put OEM toyota coils on there and NGK spark plugs.

 

I have non-denso or Asian coils I have real denso spark plugs the iridiums I've not had any problems with these coils or plugs when I had a serious miss and pulled the number two plug I could smell the coolant and I could see the rust vapor forming in that spark plug well from I guess vapor escaping past the spark plug seal or something and that vapor got all over my coil turned it orange when I took it out I cleaned it off with WD-40 and there's nothing wrong with it moved it to another cylinder it worked fine then I change the engine and put those coils in the new engine as the coils that were in the lower mileage engine that I bought or flooded in transit or something who knows they were all rusty in every well The plugs I took out of that engine were reasonably clean but I just put in my newer stuff.

 

My 2013 Prius is approaching 278K. I had my head gasket replaced about 10,000 miles ago and now it runs perfect again! I had coils, plugs, new intake manifold and EGR service done all prior to the head gasket. Maybe you should just cut to the chase and have it replaced. I found a good hybrid mechanic in Chgo who did the head gasket (including machining of the head) and a new electric water pump installed for $1475!!! I love my Uber Prius!

 

For about another $400 I put an engine that had 65 to 80K on it from Japan not even been messed with here yet luckily your mechanic inspected everything pretty good and I guess the number two holding up. I just wouldn't do that personally with an open deck engine assembly but that's just me and that's personal.

 

my experience with mechanics, they usually over promise and under deliver. After watching what Jiffylube did to their customers, it's hard to trust any mechanic on what they tell you they changed in your car

 

@Jim Caldwell your symptoms sound like the usual head gasket failure due to lack of EGR circuit cleaning. Boroscope inspection of the cylinders (for evidence of coolant leaking in) and leak-down test can confirm.

If the EGR (Exhaust Gas Recirculation) has never been cleaned it's likely near-completely carbon-choked, and the likely culprit; should be dealt with directly after the head gasket is resolved. See first link in my signature.

 

Where did you get the plugs? I would probably check them if I were you, counterfeit ones are rampant. Mine lasted only 20k before misfiring bad, they were perfect counterfeits, except worn to the bone.

 

see @Mendel Leisk 's signature above

and it's not just the egr, the four tiny ports in the intake manifold are critical as well

 

Yeah they're basically part of the EGR circuit, the final leg.

Most of the gaskets are metal, no finicky coating, and unless they're somehow bent they should be fine to reuse. The Repair Manual attachments in first link in my signature say to replace them all IIRC, but that's mostly Toyota's lawyers talking I think. However, all the gaskets at the intake manifold are pliable, and with your miles they'd worth while to replace.

That said, I'd get the head gasket assessed first (via boroscope and leak-down test). Cleaning the EGR when you've got head gasket failure symptoms (misfire on cylinder one, then two as well) is likely "closing the barn door after the horses have bolted".

FYI: the EGR passages in intake manifold (mentioned by @bisco) tend to clog unevenly: the first to be fully clog is typically cylinder one, then two, and so on. An the head gasket failure typically starts at the wall between cylinder one and two, on the cylinder one side first, and so on.

When you do get to the EGR cleaning, do check out the first link in my signature: for video and thread links, tips, Repair Manual excerpts (torque values and so on), tool list, strategies for dealing with coolant spillage (you don't need to spill a drop, contrary to the videos).

 

If you're gonna go that route I'd recommend bar's leak head-gasket sealer. Plenty of Prius owners stand by it. Search 'prius' under the question bar and you'll see reviews from Prius owners.

https://a.co/d/59poUr7

 

i'm sorry, i don't know the answer to those questions. but you're right about the overflow tank, it's just there for expansion

 

You never answered the question about the coolant level. Very important question. Definitely don't use a head gasket sealer until you have confirmed it's the head gasket, and even then I still wouldn't use it. Scotty will tell you himself, this is for people trying to be cheap with their cars. The potential for problems is just as good as the potential for fixing it. This isn't for a Gen 3 prius with 165k, it's for like a 1999 Honda Accord with 250k. The smart money is on fixing it the right way, but dear god at least don't put head gasket sealer in a car without a blown head gasket.

 

Look at you!

 

can you update us. i have similar issues an having a mechanic come out in 2days. I want to try and absorb as much ffedback as I can before they DX so i have a feel if they understand or are puffing.