2012 Prius - CEL P0301 Cylinder 1 misfire/Engine knocking - FIXED 

That Knocking sound with the Misfire P301, P302...Etc.... is do to a Head gasket, I saw many of this easy fixes on the Prius. I have a 2010 Prius with many miles and saw all this videos and ideas on how to fix the knocking and they are only temporary fixes from taking out the O ring on the reservoir to cleaning the EGR, Cleaning the manifold, and putting on new Spark plugs and Ignition coils. The best thing to do is to change the head gasket before you mess up your valves and engine. The best way you can tell is if your coolant is going down fast and check your oil. If the oil is cloudy you know something is wrong. I fixed my Head gasket and the problem is solved, it is a very large job but very doable. It took me 3 days and about $500.00 in parts.I hope this help many people that love their Prius like I do. Prius Chat helps a lot.

Thanks for sharing your repair experience. It will be very helpful when I do mine this week. Thanks again and happy Easter 👍

Great video. Clear, concise and helped me save money. Thank you!

GOOD JOB DUDE!!! Mine is hard shaking though prefers reverse and stood being crazy after about a minute. SUPER helpful. Very much appreciate you.

Hope the problem didn’t come back. Mine did the same thing. It was a blown head gasket. Took 2 weekends and 30 budweisers to change it.

In the description, you claim to have fixed the severe engine knocking; however, I noticed that 2 months later you posted a video where the severe engine knocking is still present. Perhaps you should edit this to let people know that this did not actually "fix" the severe engine knocking.

If you have the same issue, watch your coolant level. If the coolant level drops even after tipping off and you have no confirmed leaks to the outside, it is almost certain that the head gasket is going to fail in a few thousand miles and is leaking coolant into the cylinder(s) causing the misfire codes. I wasted time and money replacing plugs, coils, And cleaning EGR. Still ended up blowing and overheating my engine. The problem manifests itself more during cold weather too.

I loved this video. How you walked us through the problem, how you solved it and how much you spent. Thanks.

I just did all the intake manifold and EGR system clean at 100,000 miles on my car as a preventative maintenance job. That clip that is hard to remove took me about 1 hour. I watched a gasget masters video and they ripped it upwards, took under one second to remove. Made me feel like a fool! The underside nut on the EGR cooler didnt go back in on my car as that was a huge pain to remove. I also installed an oil catch can. Fingers crossed I dont have any engine knocking in the near future.

Great video again

Needed this so much. Thank you. I’m already $1300 in with the spark plugs, fuel injectors and ignition coils and of course the labor for each of these. But to find out that it’s still not the problem and i should have looked at this video first, I could kick myself.

I had the same P0301, engine knocking if I do not drive it overnight . Morning start ups always get a knocking for about 5 to 10 seconds. Ultimately the proper fix was the head gasket issue. Took head to the machine shop , it had some low spots. I also addressed all the things you mentioned in your video.

Great video, thanks for the reply

Oh my gosh this is EXACTLY what my Prius has been doing. Thank you so much for this video man

These are the least of his problems. I did two prius already, my brothers and mine and both times it was the headgasket needing replaced as well as cleaning the egr, egr cooler and intake manifolds tiny port holes.

Really well done! thank you!

Grate job buddy thanks for your information and vedio I have the same issue with my car 🚗 👍

I remember every once in a great while on cold startup in the morning I would hv shaking goin on. And then I wondered what if I wait for engine to shutoff (and not while its running) at end of day before pushing button to off. Ever since then I hvnt had any rattle.

I did an article on this on Prius chat. In my case the EGR pathways in the inlet manifold where blocked by soot. Only the 1st was still open. This caused the 1st cilinder to get all of the EGR gases and it started to misfire because of it... Solution: clean the EGR pathways in the inlet manifold.

Great video

If you ever have a misfire on one cylinder, simply switch the coil packs and see if the error moves with the coil.

Good job Bro!!

My wife was having this severe shaking and misfire cylinder 1 in her CT200H(same drivetrain), internet said it was the EGR. It ended up being the headgasket which bent rod #1. The local mechanic wanted $5000 to replace the gasket and Lexus wanted to replace the engine at the cost of $6500. I ended up doing it myself for about $230.

Thanks for the detailed explanation!! I’n having the same issue and have gotten as far as changing out the cyl 1 coil, and still have the problem. I’m gonna have at this and see if I can’t get this done before my car appointment in a week. Great job!

Excellent video. I thought I was the only one with this problem.

If you take a pressure washer (just go to your local car wash if you dont have one) you can clean out the EGR cooler in about 10 minutes. Easiest fastest way to go.

Olá... Sou brasileiro e seu vídeo me ajudou muito pois meu prius estava com o mesmo problema. Muito obrigado 👏🏽👏🏽👏🏽👏🏽👏🏽

Priuses are known to have that EGR issue. Best to replace the EGR and the intake. Cleaning is a pain, but depends on your budget of course. Toyota actually had a TSB and recall for a while on the EGR

Great video! Highly recommend installing an oil catch can. This will reduce the amount of oil being recirculated back into the intake manifold and clogging EGR valve and cooler. Every time I change the oil in my Prius (every 5k miles), there is at least 3-4 tablespoons of oil/fuel caught in the oil catch can. Might want to also change your spark plugs when doing this. Some of my plugs were fouled due to the excess oil being sucked back into the intake manifold and into the intake runners. Oil catch can will reduce that from happening too.

Head gasket sealer, cleaning the EGR valve, and the EGR ports cured my engine shakes. Runs like new.

id you take video or pics of how clean you got the cooler before reinstall?

My 2010 Prius just started knocking. Check engine light turned on. It has 170k miles. Damn mine does exactly the same thing. Cylinder 3 is misfiring. Any input?

Thanks your video....

Thanks COOP ...

Omg that is the SAME issue I have on a 2nd gen. With engine knock. Misfire from oil and dirty plugs but my 3rd gen also threw a code recently for this.

Very helpful

Thanks for the info as I am currently trying to remove the EGR cooler. I wasn’t real excited about removing the hex studs from the back. The bottom one is not that easy to get to as well but at least there is only that one and the top one! I have Purple Power and gas to soak it in, not sure which one will work better.

Another thing are the egr passageway INSIDE the intake manifold. You'll see these small holes in each of the runners, they lead to the egr pipe. I also used simple green, works fine.

That EGR system is a bear to do but it will save you hundreds to do it yourself. Another thing is to check your coolant level closely and often as well as the oil level. Over full will suck oil back into the manifold and EGR causing the same problem. The bonus is you will be a Prius genius after you're done.

Hey Seahawk! I know its been almost 3 years since this post. Did any of the knocking on engine start-up return in the months after doing all this? Reason I asked is because later discovery of the P0301 Cylinder misfires might have something to do with a bad head gasket.

Yes, my car has the same problem thanks

There is moisture or blow by oil getting into that cylinder , you need to check thatcylinder or have a compression check on all that cylinders. So that is the first thing to check. One of the things that have helped is cleaning out the egr pipe then adding a filtered oil catch can between the PCv valve and the intake manifold. You should clean out your intake manifold it probably has a lot of oil in it. I have high miles and changed out the head gasket and added a filtered oil catch can , I use 3 quarts of 0w20 and between oil changes I use lucus oil stabilizer , that helps with worn piston rings and oil consumption. The car no longer shakes during cold startup , no coolant loss. You can get a cheap iPhone boroscope to look into a suspected cylinder before you start up in the morning and look to see if it’s oil on the piston or coolant. Sometimes people would unpressurized the coolant system by slightly losing up the cap and selling a Prius with a bad head gasket. It will have min coolant loss and you wouldn’t notice until you drive on a hot summer day. You won’t suspect it in the cooler weather. Hope this helps somebody. My car had 223000 miles when Cylinder 2 was misfiring then I notice loss in coolant and the coolant cap was never tight or had the o ring missing. These Prius are known for burning oil because of the pcv design causing engines to start to blow head gasket and fail. There is a lot of info on priusprime forum about the 3rd gen Prius and adding a filtered oil catch can , just google it.

I have no idea if it was the fuel injection or the egr....what was the solution??

Very good

My daughter has a 2006(ll gen) and is making the same noise. Changed plugs,cleaned MAF sensor,and,intake. Still doing it.

You're awesome

So it wasn't the head gasket and this fixed the issue?

Thanks 🙏

Same thing on my 2012 prius. Dealer replaced intake manifold and all is ok. Before that replaced plugs, coils and injectors ond was still shaking.

Did this work or did you end up having to replace a head gasket? I'm asking because mine just started to do this...

This is exactly what I’m going through now

You should have recorded the dismantling process would have been great but thanks for the video

Heat shields were loose on my 2010 fixed the problem

i had the same issue but turn out to be Head gasket was leaking

can you repair my car has the same fault 2011? Please live Washington state

Great video. Unfortunately I have tried everything, manifold cleaning, new spark plugs, coils, cleaned EGR...even got a MAP sensor swap....still getting the "death rattle". All signs point to the head gasket. I saw another video that showed if you get a long pressure sound when you open your coolant reservoir, it's a head gasket issue. I suppose that's where I'll go next! 2013 Prius V 185k miles.

what is the name of that key please !

I have the same engine knocking symptoms on my 2012 Prius. The knocking only happens occasionally especially after short trips. I hope it isn't a head gasket problem. I will keep driving the car until the symptoms get more severe.

Good job well done 👏

Hello amigo, I have a question! You got the same problem back after you posted this video or that fix your car issue?

thanks you :)

This video is helpful and it is not a 'how to" video; it is a "what I did" video.

I have a 2012 Prius with 260,000 with exact same noise. I tried almost everything. Nothing worked. Until, I saw a video regarding the fuel injectors. I pulled them, had them cleaned. That was it. Problem solved. Try this first, before spending more money. I couldn't believe how easy it was to fix this yourself. Try it!!

I started using 93 Octane gas and changed the spark plugs and that fixed the problem.

I don't have engine indicator warning. But my knocking sound is terrible and car has lost total power and seems to move forward or backward at a very very slow speed. I tried replacing transmission oil and it does not solve the problem. I Almost going to replace the gearbox but in the end I told my workshop to try replacing ignition coil , Sparkplugs and the problem was solved.

Can you update this?

You indicated putting it in neutral stopped the rattling. But was the engine running anyway?

where did you get your ignition coils for $77? is that for all 4?

You had the plugs changed 30K ago so you "knew" they couldn't be the issue. Without visibly checking the plugs you cannot be sure. I once had a misfire that was caused by a piece of carbon getting jammed between the spark plug tip and the side electrode. Removal of the carbon fixed it!

Can you please put a link for the brush and wires you used to clean the EGR cooler?

this is what my moms car is doing but its leaking a TON of fuel when she starts it … could it still be a blown head gasket, or is it a fuel leak or what is it????

This same knocking is happening to my 2014 with 225k on it. Knocks at start and sometimes from stopping when the engine kicks back on. Egr was SUPPOSEDLY cleaned this year at a shop. Replaced plugs and nothing besides running a little better. I drive is hundreds of miles a day some days and thousands a month. No other engine issues have come up. Check engine has been coming on for misfire cylinder 2 but seems to resolve itself. Any tips? Bringing to the mechanic tomorrow.

Mit welchen Öl fahren sie 0w20 Oder 5w30 Welche marken Öl nehmen sie lg

What about the head gasket

Hey bro please reply I need help

I have done the same and no more rattling sound in the morning and that was bad all the pipes almost blocked now all cleaned Do CHANGE PVC it’s needed

My code says mid fire 1 and 2

I got stuck on that clip also 😂👍 well done

I strongly advise anyone doing this to replace the EGR valve instead of just cleaning it.

Can you tell its the head gasket by the misfires of the cylinders My code says 1 n 4 cylinders

Where did you ordered small twisted wires? Thanks.

I believer that you can unplug the electricity to the egr motor. If that doesn't fix it, its something else. Prob head gasket, or coil or plug if u lucky.

And im back. Put new plugs and coils(hope that wasnt a waste) in. Pray to god im not gonna hv to do all that. N for coolant I would drain maybe a third of the coolant. But knowing how the people put the prius together, sure that will be a pita to get to also.

Use BG products at least once a year after winter season. I use EPR before oil change. Then add MOA to your new oil.

So...mine did the same thing last year. Replaced egr valve, intake manifold, and even the head gasket. Only when the head gasket was replaced did the problem start. Now, a year later it’s doing it again. Any suggestions?

You can use a 6mm for that e8

I have the same exact issue, 2012 prius V. I changed sparks and coils and no change. What you think was the main cause

Do you disconnect the battery source to do this job?

Change the head gasket before you bend a rod. See "Gasket Masters" videos.

My Prius gave me 300k until I need it to do mejor repairs.

I did the same on my car But I also installed oil catch can.it will save the cat converter fro clogging .and probably will not cover the cooler. As if the engine do not Burn oil it's good for all those parts.

I have almost same problem, but mine throughing withe smoke a lot with same Knocking and help please

6 mm socket fits that stud on the side of the EGR no need for torques and it takes 20 min to remove EGR cooler max and don’t put the bottom bolt on EGR cooler

Great video I just have a question to all you in this same situation. I just want to replace pcv valve and clean the intake manifold and get a new gasket for the intake manifold. Willl that fix the rattling when the car starts

it’s common head gasket problem

how did you clean the fuel injectors?

My 2011 prius got this same cel code. Cylinder 1 misfire. What i did so far was change the spark plugs, clean throttle body, maf sensors, deep reset of engine codes, and oil change. So far ive driven the car 100 miles after maintenance was done and it still knocking on start ups. What do u recommend I should do next?

How did you really fix it? My 2012 Prius Plug-In has same issue and after trying new plugs, coils, and injectors my mechanic said I need new engine. I have 310k miles and have only done 3 oil changes until now that I change stuff listed above. So I got an engine from Junk Yard that has 88k miles and let’s hope...

These engines really do blow head gaskets. It’s not if, it’s when. People think they have fixed it, but even with “headgasket fluid repair” it’s gonna get worse.

you didn't have to drain the oil or coolant, correct?