Car knocking, changed spark plugs, problem persists

Update: After several weeks of not losing any more coolant, I opened the hood this morning to find a SLIGHT loss (it went from between the full and low line to being barely below the low). Also, I've noticed that there is coolant residue on the top of the reservoir that must have shot out from the pressure valve in the cap. I'm thinking that pressure is building up more than before? Should I consider unplugging the EGR temporarily to see if the issue resolves? I've read that as a recommendation in a separate post on this issue.

Ever since the weather has risen above 50 degrees Fahrenheit, the misfiring upon start-up has disappeared. It seems to be linked to temperature.

 

I would certainly message/email/call Toyota and give a complaint about this. Maybe if enough of us complain they will take the 3rd gen misfiring seriously. I'm about ready to sell mine and go find a 2nd gen, personally. How much coolant are you losing over the period of a week? Since it is a continuous leak, if there are no visible indications of coolant in the engine bay or on the pavement then I'd say it's a good bet you've blown a head gasket. How many miles do you have on your car?

 

Sounds like an improvement. You will need to clean the egr valve and egr cooler as well. Good luck!

 

NutzAboutBolts has a ton of Prius relevant videos that are really informative, btw.

 

Update: Tonight I removed the throttle body and intake manifold to clean. Changed the PCV valve as well. Planning on installing an oil catch can, but I have to wait until I can find a 3/4 to 1/2 hose adapter. I'm attaching a picture of one of the intake ports to show how gunked up it is. I'm not entirely sure what to do. I tried using a flat-head to very carefully scrap some of the carbon off. I don't feel comfortable going any further for fear of knocking chunks down into the valves.

I've been using purple power and water to rinse it out, but not getting much carbon out. It looks similar to the intake ports in terms of carbon buildup. I didn't want to use brakleen or carb cleaner since it's plastic. Any ideas on proper way to clean intake?

Also of note: I noticed the buildup in the 2nd port (2nd from the passenger side) was sludgier/oily than the rest... not sure if that's important or not.

54434740_413818082527682_4520876481211006976_n by Jacob Bonner posted Mar 22, 2019 at 12:04 AM

 

Isn't the intake manifold plastic? I would use carb cleaner but I keep reading to avoid plastic with it. I might have to. I didn't realize how serious the intake manifold cleaning was until I saw this video:

 

So I'm mentally preparing for replacing the head gasket after this semester. I noticed white steam coming from the tailpipe this evening (while running the heater on full blast) and the cylinder misfiring is only getting worse. One of my questions is: should I consider lapping the valves even though it's a 2012, while I have it broken down? I don't want to put more work on myself if it's not really necessary. Is this something I can do with a drill and suction cup? I've seen others do this, but then I've heard others claim that this is a bad idea because of minor wobbles that the drill makes.

Also, should I inspect for a cracked valve cover or cracked cylinder head or both (how would one go about this?)? I admit I'm a novice, but I don't have the money to pay someone to fix this. Is the block itself aluminum?

Do I need to replace any of the coolant hoses? I have read elsewhere that that may be necessary if oil has mixed.

 

Just an update: I've taken the EGR cooler and valve off and cleaned them. Oxyclean and pressure washer worked wonders on the cooler. I used carb cleaner on the valve though. Car still knocks, as I expected. While I had the windshield cowl off I switched the ignition coils around and oddly enough the misfiring has switched cylinders... could this be an indication that the problem is with the coils? If it matters, originally I had misfires on the 1st and 2nd cylinders, then I swapped the 2nd & 3rd ignition coils. Immediately I started getting 2nd & 4th misfires (if my memory is correct) -- not what one would expect. Then, as I said, the other day I swapped 2 back with 3 again, but also swapped 1 with 4. After this exchange, the misfires have been exclusively on 4. If it were a blown head gasket, wouldn't the misfires remain on consistent cylinders? I might try to replace a coil or two and see if that fixes my problem. If not, head gasket it is... there still is the matter of consistently losing a small amount of coolant.

Also, all four coils have this rusty colored marking on them. What should I make of this, if anything?

 

The EGR was about as bad as some of the others I've seen here. Couldn't see light through it -- could barely make out the individual spacers inside the cooler. The plunger in the EGR valve was tight and could barely move by itself. After some carb cleaner and silicone spray, it moves just fine now. It has 175k miles on it, so that was expected. I soaked the cooler in oxiclean maybe 5 times in 5-7 hour intervals. At first I was using a water hose on it, with no substantial results. Finally, I used a pressure washer on it and within 5 minutes it was spotless. The pressure washer is the key to this process, though I'm sure the oxiclean soaks helped to loosen the carbon. I'm planning on re-cleaning my intake manifold, this time with a similar method, as the first time I simply used a water hose and purple power.

I just bought a set of 4 Denso ignition coils off eBay for about $60 for the set. I was surprised at the price difference between eBay and Amazon on these. They're listed on Amazon at $80 per coil. I'll let everyone know if this solves my problem. I think I've figured out where my coolant is going. I looked at the reservoir this afternoon and pink coolant crust was all over the reservoir and down the side of the engine bay, so it must be leaking out of the pressure valve. I had previously assumed it was going into the cylinders.

I recently bought the OBDLinkMX+ code/data reader off Amazon so I could monitor my engine and coolant temperatures. Most of the time it stays in the 190°-198° Fahrenheit range while driving. However, I happened to open up my OBD app to check the engine temps and they were up to 235°, so I stopped the vehicle and let it cool down. After resuming my drive, the temps stayed in the 190-198 range the rest of the time. I have had this happen a couple of times before when the coolant temp light would come on briefly. I guess it's time to replace my water pump.