P0300 0301 0303 misfire and engine knock problem

Leaky leakdown tester. What is the world coming to?

 

Sounds like it's the head gasket, unfortunately.

If you had damaged the EGR system, you would likely see where coolant was leaking, or could hear where exhaust gas was leaking. Or are you thinking it's possible that coolant is going into the EGR gasses via a cracked EGR cooler--maybe check the egr pipe to see if it's wet. You'd probably see lots of white smoke in this case.

What codes are you getting? Misfiring on all 4 cylinders?

 

I'm dealing with the exact same issue. No remedy yet. Thanks for sharing your efforts!

Engine rattle at low RPMs with some load, even on startup now. Once the engine speeds up a bit, the issue is gone and there's no detectable loss of power/torque until it's slow again, then I get it again intermittently. Feels like the engine is trying to shake itself off the frame!

I replaced the spark plugs / coils. Opened up the EGR valve and it moves super smoothly. Removed the the pipe in front of it and it wasn't clogged (had maybe 1mm of carbon buildup). I blew compressed air in while pushing the EGR valve, and it sounds like air moves smoothly, and changes resonant note when I push the EGR valve, so it's not clogged.

What next?

My non-Prius car guy is convinced it's the transmission slipping/chattering. But he also thinks that'll be a repair that costs more than the value of the vehicle. I've seen no indication here that it's the transmission and he can't prove it.

The Toyota dealership wants $400+ just to start to diagnose it.

 

I’d say it’s either a clogged EGR cooler, or the head gasket.

it’s definitely not the transmission. The Prius uses a very simple but elegant planetary gear set utilizing two electric motors. Basically the only way for them to fail is an electrical short which is very rare.

 

Check/clean the intake manifold too, in particular the EGR passages: large EGR intake passage feeds into four capillaries, one per port.

 

...and while you have the intake manifold off, put in a new PCV valve.

How many miles are on the car?

 

@pjksr02 There are 168,000 miles on the car

Thanks so much for the advice! That's super valuable to hear. I'm so glad it's not the transmission.

How can I know if it's the head gasket or not? The coolant level was mid-way - haven't been driving it a ton so I don't know if it's eating coolant.

So my half-way EGR check that showed the valve and front tube just wasn't enough? It sure looked like air could flow.

Both issues seem like pretty substantial projects. I would love to figure out which problem is causing the issue before I go fixing the one that isn't.

 

EGR and intake manifold cleaning are not that hard. Head gasket is tough. Independent shops would charge around $2500?

Leak down test is good to diagnose if head gasket is failing.

 

With the miles it’s a good chance It’s the head gasket. A proper test would be the leak down test, as stated above.

you might try loosing the cap on the coolant fill reservoir to depressurize the coolant system. Drive around for a bit with the reservoir cap loose end and see if the shaking stops. If it stops that’s a good indication that your head gasket is leaking.

As far as the EGR cooler I can promise you it has a good bit of carbon buildup at your mileage, so just keep that in mind, not saying it is for sure the cooler but there’s a good possibility

 

Buy a cheap little borescope and remove the spark plugs and see if there is liquid running down the cylinder wall. Make sure you do this after driving for a while to pressurize the coolant system. I had a similar issue and did all the same steps. I actually missed it the first time because i scoped it when the car was cool. I had a small drip forming on cylinder #2. I could watch it form a drip and then run down the cylinder.

 

Thank you all sooo much for the advice. I tried opening the coolant tank cap as @Aaron Vitolins suggested, and it worked! After an initial vibration, I was able to drive without more vibrations. Which, while pleasant, is probably a bad sign. Yes? Also, noticed the engine coolant level in the reservoir has gotten low.

Does that mean it's the head gasket? I have a fellow I typically take the cars to, but he doesn't know the Prius' idiosyncrasies. He doesn't do a leak down test, but he does a pressure test on the coolant system. I left it with him for that, but apparently his equipment won't fit the cap without some magic adapter he doesn't have yet.

Is it worth buying a leak down tester and figuring out how to test it myself? Is it most-likely the head gasket?

What do you recommend at this point? The car has a list of other things it needs (brakes, tires) and I'm debating if it's time to sell it vs fix it. The laundry list seemed reasonable, but probably not on top of a multi-thousand-dollar engine repair. How do I know when it's time to cut bait?

I'll still be driving another Prius, even if this one finds a new home.

 

I would definitely say that’s your head gasket, especially since it’s so common. Not worth spending the money for the official test. With the cap loose, it will stop the leak for now, but the coolant level will keep going down, due to it not being a pressurized system now. So I’d top it off maybe once a week depending on how much you drive.

it might be time to sell this Prius, depending how much you like this Prius. Or maybe buy a new one, I’m sure you could get a pretty good deal.

 

K-Seal?

moto g(7) power ?

 

And people give me a hard time when I say don't purchase a used Gen 3.......