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Knock misfire issue?

Tiny
BHAMDOC1973
  • MEMBER
  • 2010 TOYOTA PRIUS
  • 4 CYL
  • 2WD
  • AUTOMATIC
  • 163,000 MILES
I have had my share of these car issues before and was able to fix them. I had one before that was knocking on startup and I replaced the EGR, EGR cooler, updated intake, fresh coolant, new plugs and coils and some fuel system cleaner in the tank. This one here has same knock, I started with the plugs, injectors and coils, still misfiring and it moves from sometimes being cylinders 1, 2 or 4, randomly. I put it in maintenance mode and let it run for hours with fuel system cleaner in tank, still doing it. It can idle fine and run smoothly for minutes then all of a sudden It starts to knock then goes back to normal. Oh, I also changed the PCV, cleaned the intake, cleaned the EGR cooler and EGR. Same results, decided to replace EGR, same results, got another set of injectors same result. Coolant pressure test showed normal with no issues. And no coolant loss.
Not sure if the intake was not cleaned enough or if a really dirty EGR cooler can cause this.
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Tuesday, June 27th, 2023 AT 3:52 PM

20 Replies

Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 47,602 POSTS
Can you please shoot a quick video with your phone so I can hear the noise? That way I can tell for sure what's going on. You can upload it here with your response. It sounds like you may have a broken valve spring. I would remove the valve cover and check, here are the instructions to help you.

This guide may help as well:

https://www.2carpros.com/articles/understanding-and-repairing-engine-knocking-noise-an-in-depth-guide

and

https://www.2carpros.com/articles/engine-misfires-or-runs-rough

Let us know what happens and please upload pictures or videos of the problem so we can see what's going on.

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Wednesday, June 28th, 2023 AT 12:36 PM
Tiny
BHAMDOC1973
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I will shoot a video, but I think if it was a broken spring noise will be there all day not when you first start then smooths out and comes back later.
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Wednesday, June 28th, 2023 AT 12:44 PM
Tiny
BHAMDOC1973
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Attached.
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Wednesday, June 28th, 2023 AT 2:05 PM
Tiny
KEN L
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Thanks for the video, you are right the engine is okay and I don't is it misfiring, it sounds more like the Hybrid transmission front planetary or possibly the input shaft can you tell if the engine is coming from behind the engine and in the transmission area? Here is what I am talking about. The noise can cause the knock sensor to go off and cause the engine to become unbalanced which can cause the random misfire codes. Check out the images (below). Please let us know what happens.
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Thursday, June 29th, 2023 AT 10:28 AM
Tiny
BHAMDOC1973
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  • 1,573 POSTS
You mean is the sound coming from around where transmission meets the engine?
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Thursday, June 29th, 2023 AT 10:47 AM
Tiny
BHAMDOC1973
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  • 1,573 POSTS
Feels like it's coming from the back, but there is no vibration while I am driving, so what are the possibilities? How can I check on mounts on this vehicle like we did with regular cars by pressing gas and brake pedals since it's hybrid?
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Thursday, June 29th, 2023 AT 11:14 AM
Tiny
KEN L
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Yep, that is one way, also you can try lifting the engine or transmission with a floor jack to see if there is excess movement. I don't think it is an engine mount, but you never know. Does the noise change when shifting from park to drive to reverse?
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Friday, June 30th, 2023 AT 9:57 AM
Tiny
BHAMDOC1973
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No, I don't feel any jerk or change when I change to drive or reverse, I never had a Prius that had an engine mount.
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Friday, June 30th, 2023 AT 10:01 AM
Tiny
KEN L
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I wonder if you do a CAN scan if anything comes up. You can get a CAN scanner (Controller Area Network) which will work on most cars from Amazon.

here is a video to show you how:

https://youtu.be/u-4syLc-ifQ

Please go over these guides and get back to us.
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Saturday, July 1st, 2023 AT 11:18 AM
Tiny
BHAMDOC1973
  • MEMBER
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I kept playing with swapping coils and plugs then swapped injectors from a cylinder to the other now its running good, just a 1/2 of knock upon starting, maybe one of the injectors wasn't spraying right on connector not 100% placed, been running 30 minutes now with hardly any knock.
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Sunday, July 2nd, 2023 AT 7:18 AM
Tiny
KEN L
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Hmm, I wonder if the engine is detonating. If you remove the spark plugs, what do they look like? You might have a plug that has come apart.
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Monday, July 3rd, 2023 AT 12:31 PM
Tiny
BHAMDOC1973
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Possible, I bought them new though. I thought about replacing it again, but it keeps going back to cylinder one as far as misfire. Today I did a leak down test, it was perfect. And the valves were clean when I removed and cleaned the intake. Driving me crazy. I wish there was a way to know if is not so clean EGR cooler could do this.
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Monday, July 3rd, 2023 AT 1:22 PM
Tiny
KEN L
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I would remove the valve cover and check the cam lobes/valve train you could have a camshaft going flat.
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Tuesday, July 4th, 2023 AT 9:49 AM
Tiny
BHAMDOC1973
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If it did, wouldn't the noise be there all day long?
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Tuesday, July 4th, 2023 AT 9:58 AM
Tiny
KEN L
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If the noise has just begun then it could be cold only at first and then wear further to be present at all times. I still think it could be the coupler between the engine and transmission. Can you get a video of the noise from under the car?
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Wednesday, July 5th, 2023 AT 9:31 AM
Tiny
BHAMDOC1973
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Attached. Started the day bit not as bad as before.
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Thursday, July 6th, 2023 AT 6:23 AM
Tiny
KEN L
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Thanks for the video. Yep, that is a good one. I will ask my other experts if they have heard the problem and get their input.
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Friday, July 7th, 2023 AT 9:37 AM
Tiny
JIS001
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Hi, I see from your earlier post that you did a coolant pressure test. Do you have a bore scope to look inside the cylinder? Normally #2 cylinder will be the one leaking coolant. If you don't have one maybe an auto parts store can rent, you one.
Also, if you have an enhanced scanner go to Mode 6 data and look at your misfire monitor. If you have a high number in one cylinder swap over the coils, plugs, injectors like you have earlier. Reset the check engine and see if the misfire follows. Mode 6 is really good data for intermittent faults like the misfire you are getting intermittently.
I have provided a video on a head gasket leak I had on a CT200H. Same thing, random and coolant wasn't low. Maybe someone topped it off? I didn't even need to pressure test it. Just warmed up the engine. Hope this information helps you out and let us know what you find once you get the Mode 6 data.
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Friday, July 7th, 2023 AT 11:54 PM
Tiny
BHAMDOC1973
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I have a good camera and I thought that was the issue, but there is nothing on the walls or cylinders and the pressure held all day as far as a leak down test. Also, I didn't have to top off water since I did all that and drove it 350 miles. Keeps giving me cylinder 1, then when I switched all gave me 2 then 1 and 2, its random not always same cylinder. Sometimes the misfire is there, sometimes not. The misfire count is around 15-20 on cylinder 1, and then maybe 2 on cylinder 2. Then after a couple of seconds all are zero. Oil looks good, coolant is where it should after all the driving, weird.
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Saturday, July 8th, 2023 AT 3:13 AM
Tiny
JIS001
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I would recommend you do a leak down test next to see. If you see any bubbles in the cooling system.

Also, I would like to know what the test ID results are on the misfire monitor when you access mode 6. That section keeps track of your current and previous misfires. If you have zero misfires say on #1 at your misfire counter data, in mode 6 data looking at the misfire test monitor it will show you all the misfires it is keeping track of. You may see a high count under previous or even current. That info is more accurate since it keeps track. And as stated earlier if you see a high count on say #1 cylinder swap the coil or plug over to #3 and then clear the light like your resetting codes and see if those numbers follow your component, you moved over.
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Saturday, July 8th, 2023 AT 7:06 AM

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