Misfiring or something else?

So I have a 2004 prius with 272k miles. I don't know what package, but it has navigation & JBL speakers but no backup cam.

About 2 months ago, I was driving it one morning, and about 3 miles out, suddenly the car sounded different. From that point forward, I realized that when the ICE was on low rpm, the car would rumble like I had a huge subwoofer, and I was hearing some sort of sound like a piece of metal rattling about in the engine (brings to mind a visual like a leaf blowing about in the wind, but instead of a leaf, its a piece of metal).

Here's a recording I took (you can probably hear my blinker as well, but its mostly rattle - best heard at around 30 second mark).

I did some searching on priuschat, and I couldn't find anything other than some people saying the gen 3 had a manifold issue (with a TSB issued, then retracted) but it seemed to be only cold startups, and the video I saw didn't seem to match the sound I heard.
I also found someone that said that once he put it up on a lift he found a piece of metal jammed between something & something. I took a look under my car after jacking it up but couldn't find anything that seemed out of place.
I also looked a bit at the possibility of a bad engine mount but I couldn't really figure out how to determine if it was really bad and it didn't seem like the engine was moving too much when it would start up.
I stopped by a mechanic that said it might be exhaust related but he said I should come back the next day so he can put it on the lift and bang around a bit. I came back the next day and he said come back again. I did and he said come back again... I kinda got fed up so didn't go back.

Last week, suddenly it got much worse - the whole car started to shake violently, and engine power was noticeably reduced and now car felt like it had a bad clutch or something - every time I would hit the gas it would sound like its struggling. I resorted to flooring it to get myself to like 50mph and then would coast. But I noticed the engine having difficulty, and exhaust smell + definite smell of gasoline. Check engine light blinked a few times and then came on, and I pulled a code of 3001. So now its clear my engine is misfiring. And it is doing so on cylinder 1.

I drove a bit more (didn't have much of a choice unless I wanted to tow) and managed to pull more codes/pending codes - p3000, p3001, 3002, 3004. I don't recall which were pending and which were set.

I then came straight to PriusChat and started reading.

I had previously changed my spark plugs & pcv valve at 255k miles with the Denso SK16R11 plugs. When changing the plugs, I noticed that plug 1 (most left when facing windshield) had a bit of oil on it on the ceramic part (where the coil goes). This made me concerned that I had a blown headgasket, but after some reading on priuschat it seemed to indicate I needed to change the valvecover gasket - and I saw that a different guy here had a LOT of oil on his - I had very little on mine - maybe like enough to stain (not drench) a quarter sized circle on a paper towel. Nevertheless, since I now had a misfire, I was concerned about it, so I decided to pull the spark plug and see what was going on.

Here are some pictures, including pictures of the inside of the cylinder. https://goo.gl/photos/3bduRCejz6o2juXo6

I noticed that the plug looked almost wet (seems like more oil than last time), and the tip looks blackish - which according to this guide that I now found after the fact: 2carpros .com/articles/engine-misfires-or-runs-rough - it might be called a "fouled" plug. It should be noted that this was my first spark plug change when I put these in, and I did use anti-seize - and slight possibility that I may have used too much? You guys would probably know better than I would.
I also noticed that the back tip - where the coil meets the plug by the white ceramic looks like the metal has been worn down it is a lighter gray color at the tip.

It didn't seem like an absolutely obvious issue with the plug to say it would be the cause of misfiring, so I just cleaned off the plug and put it back. I had read that a troubleshooting technique would be to swap the coil with a different cyl, so I swapped #1 with #3, and cleared the check engine.

I also got a bottle of techron and poured that into my recently filled tank hoping that would just clear out a clogged injector. I had cleaned the MAF sensor & throttle body at 254k miles and used a bottle of techron then too so I didn't look at these to see if they're dirty again ( maybe I should though..)

At this point, the check engine light indeed seemed to switch to cyl 3 (p3003) yet i still got pending codes for some of the other cylinders. This made me believe that indeed the coil was bad, so I bit the bullet and went out and bought a coil. I took coil 3 that was now in cyl 1 and put it back in 3 and put aside what was previously coil 1 and put the new coil (I bought the Denso) into cyl 1. No improvement. I then decided to put coil 3 back into cyl 1 and put the new one into #3.
This stopped the shaking, stuttering & check engine lights.
But now we were back to where we started - the sound of a piece of metal rattling around in the engine.
I decided to buy another coil and put it in cyl 1 (if cyl 3 misfiring was fixed with a new coil, it would stand to reason that putting the coil that was on cyl 3 onto cyl 1 would be a defective coil). This did not change anything. I then tried putting the new coil in all the other cylinders without any improvement.

At an impasse, I went to autozone and borrowed a compression tester. This morning I pulled out all the plugs, unplugged all the coils, and put compression tester in cyl 1, turned the car on, and cranked it by pressing the gas. Check engine came on, but compression guage showed about 90. Repeated on the other 3, and got about 90 on 2 & 3 and 97 on the 4th - I realized later that the gauge jumps from 90 to 120 very quickly so it could be the first 3 were actually a bit more than 90.

As per other threads on compression testing it seems most got 125+ when doing this. So I don't know if all cylinders are just evenly worn (as per Patrick) but still a problem, or the compression tester wasn't really tight enough in the cylinder (seemed to turn forever, never getting "tight") or the compression tester is just calibrated incorrectly.

Either way at this point I'm at a loss on what to do now. Anyone have any ideas?


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Background info that may be useful:

• Pictures of spark plugs that were swapped out at 255k https://goo.gl/photos/QnxR4LP4Lc8481GC7 that may be useful to diagnose engine (I took these pictures a few days ago, as I had held on to the plugs, so some things that may have been there then may have dried out)
• Pictures of The recently installed plugs that I pulled out today for the compression test https://goo.gl/photos/TSeNZaegkPvhnDPq7
• I did check the 12v battery - I got 11.96v on the diag mode screen before car turned on and 14 or so once ready.
• Muffler was replaced at around 256k miles
• Some date from torque app testing mode: Gen2 Prius: Custom PIDs for Torque (Android App) with formulas | Page 32 | PriusChat

 

Patrick,

Thanks for your response.

2. Yes, it was definitely the misfire code when I looked it up.- I must have remembered incorrectly the exact code.
4. Rattle occurs only when the engine is on - more pronounced when in drive. I think Luscious garage has a post somewhere that says that misfires can cause something to hit something (maybe some sort of rod hitting transaxle) which causes a type of noise which may be what I'm hearing. If I find post again I'll edit to include link.

I'll look into the other suggestions you've posted - it may be beyond what I am able to do on my own.

 

Patrick,

Can you comment on the condition of my spark plugs from the pictures? thx!

 

This has never happened to me. Previous owner seemed pretty meticulous about maintenance - most work was done at dealer, and 2 years later he still emails me and asks how his baby the prius is doing.

I decided to just now go out and check the oil - Car was driven about half hour ago for 10 minutes. Oil level is about half way between bottom two dots on dipstick.

I also happened to bump into my neighbor that used to be a used car dealer & buy cars at auction - he said my oil is a little bit dirty but he didn't see any tiny metal fragments that indicate wearing down or smell any burned smell. He also asked me if the tailpipe is spewing white smoke which indicates a blown head gasket - I haven't seen anything like that.

I last changed oil at dealer about 1400 miles (4 months) ago.

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Since I last posted I have tried the following steps ( I did not yet have the time to do any of the other suggestions by Patrick):

I decided to put back what I thought was the defective coil, and it seems that the check engine light & super bad misfiring didn't return. So it seems like coils are not the problem...

Also, I will try to redo the compression test sometime next week after warming up the engine. We'll see what the results are.

 

Oh and I found the luscious garage video that says "When Prius misfire the planetary gearset in the transmission slaps around, which can sound like a rod knock. "

 

Thank you Patrick.

Based on this https://www.facebook.com/pg/LusciousGarage/photos/?tab=album&album_id=309872492465859 I'm starting to suspect the intake manifold. How do I test it without a smoke machine...?

 

I certainly hope you're wrong. If you're right what can I do to keep the engine alive as long as possible? What oil do you recommend instead?

Also, the prius is well known to hit the 350k -450k mark without a problem, and my understanding is that it is usually something other then the engine that is not worth fixing - why do you believe it would be severely worn just because I'm at 272k? I understand somewhat worn, but severely?

 

I wouldn't mind removing the intake manifold if it takes less than an hour to do - I'm comfortable doing most things, just I don't have a driveway to work in nor do I have someone to help me so anything I do needs to be able to done by myself without needing more than a basic mechanics toolset. Once I'm removing it, I'm assuming I might as well clean it and maybe clean/adjust something else? Should I change the gasket? My understanding is that the Gen 3 actually has some sort of TSB about this...

Regarding gasoline vapor, I'm not sure if I smelled it in the car or only once I stepped out after driving it.