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

well done, thank you!

 

So the implication here is that cleaning out the EGR system solved the cold start misfire problem commonly referred to (in error, I suspect) as "knocking"?

I have a hard time believing that EGR is active at cold start or cold idle, so I wonder if the cold start problem is an EGR valve sticking open.

Has anyone ever seen the EGR valve mapping (on engine load vs RPM) or collected data to observe it's action during startup? Anyone ever disassembled the EGR system and discovered a valve stuck open?

1st time poster here... bought a 2010 ver II for my daughter a few weeks ago, 98 K miles to start, nearing 100K now, I've been lurking here since.

FWIW, no oil burning to speak of, "one half shop rags worth" of oil pooled beneath throttle body, a little coking in the EGR pipe, runs great so far. My PM plan includes an IM cleanout soon, PCV valve replacement and OCC install at same time (just because easy), full EGR cleaning and plugs next Summer.

Maybe I'll get lucky and she'll get herself a mechanically ept BF first.

 

Here’s my experience with obd2 code p0301

2012 Prius Plug In 247k miles

I changed out the original spark plugs at 238k miles. I did not change the coils. The og plugs looked great, no oil no water.
p0301 is the first CEL code this car has ever thrown, and it happened right at 247k miles. The first time it gave that code, I did nothing and it went away on its’ own. Second time it threw that code, I added half a can of Seafoam to a full tank of gas, put the car in “Power” mode, and drove the shit out of it; fast at high rpm. The CEL went away on its’ own almost immediately, but 0301 is still in monitor phase.

I’m trying this first, because taking off the wipers and cowling is such a pain in the nice person!

With corona hitting, my 2012 Prius plug in went from 800++ miles a week of freeway driving, to <100 miles a week of all EV driving.....so I’m hoping I caught this early, and that the seafoam will help. I’m gonna drive it waaay past the add fuel notification. Power mode seems like it’s just too easy of a fix, right? Keeping it a high rpm avoids the shake shudder knock associated with p0301.
I have maintained a gen 2, gen 3, and gen 4 for 500k miles, thanks to the awesome folks here on PriusChat! What these cars need more than anything is to be driven.... A LOT! So, road trip time! I will update.

 

No luck :-( p0301 is back. Knocking from the engine is pretty bad. I’ve got her taken apart, working on cleaning the EGR pipe. Anyone have any suggestions how to clean the egr and cooler without having to remove them?
I’ve had a little luck with a vacuum cleaner, just sucking where the egr pipe hits the “elbow”. I know it’s probably not doing too much.

 

Sorry to hear this.

The misfire code is unfortunately usually indicative of a head gasket failure - - of coolant getting into the misfiring cylinder.

You can clean your entire EGR system (cooler, valve, pipe and intake manifold), and hope for the best. And, you may try a head gasket sealer. But, most folks here, with the misfire code, have found that the head gasket is failed.

The best test for the head gasket is a leak-down test.

Wish it wasn't so.

 

Yeah hoping it’s not the head gasket. I tried the car’s heat today. It was super toasty, very hot, and working. Isn’t no heat usually a sign of bad head gasket? I’m hoping that cleaning the egr cooler, cleaning the intake manifold, and putting in a new pcv valve will buy me another 50k miles... even if I have to add coolant occasionally. Pre covid my ‘12 Prius was driven 30k+ yearly. I bought it used in ‘15 with 91k. For me to ‘get my money’s worth’ out of this car I’ve gotta get to 300k. Next smog isn’t due til 2022...so....

 

Sounds like you got your money’s worth already...

No heat is only an issue if the levels go below the low mark and has excessive air in the system.

Additional signs of head gasket failure:
Loss of coolant in reservoir. Subtle, but if issue has been ongoing, it’ll be below the plastic seam line.
Check top of pistons (through spark plug holes). Look for “wet” piston top in misfiring cylinder.
While you’re at it, check plugs and swap plug order to see if the issue follows the plug or stays with the same cylinder.
What typically happens is the headgasket fails between the piston and coolant channel. When warmed up, the gasket is expanded enough to seal properly (until it gets really bad), but when it cools down, the pistons vacuums a little coolant into the cylinder. The little bit of coolant causes the rough cold start, but after a few seconda of burning it off, runs fine until the next cold start. Sometimes it doesn’t have to cool down all the way, just enough for the coolant to seep in.

Also, being a PIP, switching your EV mode for an extended period of time will also allow coolant to seep into the cylinder while the gas engine cools down.

Good luck!

 

I did the intake manifold, pcv, and egr cooler. Running alright now for 100 miles, but a pending p0301, no actual CEL yet. We’ll see....

 

What you might "see" is a hole in the engine block, if sufficient coolant gets into a cylinder (typically cylinder 1) that the piston can't compress, the piston arm breaks, or the crankshaft fails.

Nice digs btw.

 

I reckon I’m pretty screwed... eh? Nutz feel like doing a head gasket video? I’ll drive up north to you, and help with the video.

anyone recommend a gasket sealant ? Some thing not too expensive that I can pour into the radiator reservoir? I haven’t done a real ‘scientific’ measurement of the amount of coolant I’m losing, but it doesn’t appear to be too much. Just drove 75 miles, including 20 miles at 60Mph straight up hill from 1,000’ to 5,500’ and no significant loss of coolant. But, the knocks and dreaded CEL p0301 are back, this time with p0012 “over retarded camshaft oil sensor”?
I did the air intake, pcv, and egr cooler, and want to try a gasket sealant product. Doesn’t seem like my HG is too far gone...yet.
She drives great, until EV mode kicks in and the engine cools down. I kinda wish there was a charge inhibitor mod like I used to have on my 2000 Honda Insight 5 speed. It was a switch that tapped into the cars sensor to tell when the clutch was depressed. Can we figure something out with the Prius to make the hybrid system think the car is in neutral and not regen charge? My plug in goes from empty to full charge just by driving down from the mountains, and the misfiring / knocks don’t really begin until the engine has cooled back down from 9 miles of EV driving.

 

What happen to the hydro lock scared straight scenario?

 

No sure were you're at in the failure process, but some find temporary relief by loosening the cap on the coolant tank. YMMV.

 

There have been people who have used gasket sealant. Seems to work. Some have had it work with no issues, while others had it work by sealing the head leak, but also clogging other areas. It's really a gamble at best.

 

Can't remember if I've mentioned gasket master videos before; worth a watch:

New head gasket replacement video from Gasket Masters | PriusChat

 

So... I seriously doubt you blew your block/piston/rod, because you'd know it. lol. But I do believe your head gasket is leaking. While you mention this one trip, it's not that quick. I'm talking a tank every few dozen or so cold starts. It's when the engine cools down that it leaks into the cylinder, not when you're running.

Do you recall how high (photos or something) the coolant was when cold anytime before all this started? Use that as a baseline to compare where it is today vs. then. Odds are, if you're an inch or more below the plastic seam, you're lower than you were before and I can talk you through how to "seal" the gasket temporarily w/o clogging other parts of your coolant loop.

 

By remove the O ring from the cap, and reinstalled the cap back.. I believe now you have a non-pressurized system..

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Another possibility on these types of "knocks" or "shakes", beyond the very commonly mentioned: HEAD GASKET, EGR system/intake, fuel injectors, plugs/coils/PCV..., is the DAMPER ASSEMBLY / Transmission Input (31270-47060).

As having recently experienced weird knocks/shakes on my 2010 (mine wound up being the DAMPER), my troubleshooting steps for any 3G Prius knocks/shakes would be as follows:

- run compression A/O leak-down tests to assure head gasket integrity [replace if necessary]
- clean intake/EGR system
[- check/clean/replace fuel injector(s)]
- replace plugs/coils/PCV
- replace damper assembly

and that's because that is in order from cheapest to most expensive to have done (if taking car to a shop). It should not cost much to have the integrity of a head gasket checked, or of course FREE if you or a friend are DIYers and you or someone you know already has the tools to run compression / leak-down tests! So, just checking the H/G integrity is FREE-to-CHEAP - of course if you find out it is FAULTY, it's of course going to be a rather EXPENSIVE fix, though VERY worth it if you're not a DIYer. Not too expensive to fix if you plan on doing it yourself! (Also, best to know early on about such an expensive/in depth repair being needed! For example, why continue on if you're not willing or able to facilitate such an in depth repair!) Next up, cleaning the EGR system and/or intake - also should be FREE-to-CHEAP whether you DIY or have a shop do it! Testing and cleaning stuff (at least where I live) always costs a lot less than replacing stuff! But if you've already verified the integrity of the H/G (don't forget if DIY replace it, you still have to run compression/leak-down tests after doing the job to make sure you "did the job" right!) and have cleaned the EGR and intake systems, next I'd replace the plugs, coils, and the PCV valve! If all else fails, and there are still weird 'knocks' or 'shakes' at this point, the only other thing I (personally) know that could be the culprit would be the DAMPER ASSEMBLY. Not too much for the part itself, especially if you order straight from Japan, but the LABOR on this job is just as bad (if not worse) than having to replace a HEAD GASKET!!! The part MSRP's for something like $900 (US), but it can easily be found for something around $600 from American (US) sources, I got mine straight out of Japan for like $300! Labor for that job set me back ~$1000 (just about on par with what labor would be on a H/G)!

The only thing I didn't really mention was the fuel injectors. Reason for that was because I could have sworn those could/should/would throw their own separate DTC codes, which should really separate them from your "common" misfire codes, which I know you can get from faulty Head Gasket, dirty EGR/intake, faulty plugs/coils/PCV, faulty Damper Assembly... If anything I'd add that step (checking/cleaning/replacing injectors) AFTER cleaning the EGR/intake, and BEFORE replacing plugs/coils/PCV... I never ended up "checking" or "cleaning" (or replacing) mine since there was never any injector specific DTC codes thrown, and replacing the damper solved my issue!

It also "stinks" that the damper isn't really something you can easily "check" or "test", the ONLY way to LOOK AT and SEE IT, are to split the motor and the trans... Unlike the Head Gasket, which can be "checked" very easily by running leak-down and/or compression tests, and all the other "stuff" that can just be "checked" and/or "cleaned" and/or "replaced" rather easily! So if you're going to "check" it, you may as well replace it "while you're in there", since you have to split the motor and the transmission just to see it anyway! Also why it's last on the list, even "checking" it without intent to replace unless "bad" would be VERY hard and labor-some! For this reason, it made last on my list, and I wouldn't go in there just to "check it", if I go in there (or am paying someone else to, like a shop) it's not going to be "just to look", may as well replace it while in there!

Notes: The DAMPER ASSEMBLY is where you'd normally find a "clutch" or a "torque converter" on a "traditional car"... It has the job of absorbing all the "shock" between the motor and the trans (input shaft) every time the motor kicks on and off (ESPECIALLY while the vehicle is in motion)!

 

Have you had an actual compression (and/or) leak-down test performed to CONFIRM the integrity of the Head Gasket??? If you haven't yet, do yourself a favor and do that ASAP (ESPECIALLY before adding any really nasty crap like "gasket sealer")! I say this because, in your quote, highlighted in RED, is the EXACT SAME SYMPTOM of a faulty DAMPER ASSEMBLY!!!

 

They're actually members here now I believe: @Gasket masters .