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Discussion Starter · #1 ·
Hello everyone.
I recently tackled the spark plug change and resealing of the water inlet in my 05 sienna. I used Denso 3297 iridium spark plugs. I didn’t change ignition coils. I used new felpro gaskets for the plenum, intake manifold and throttle body. I sealed the water inlet with permatex optimum grey rtv. I also changed the knock sensor harness. I made sure I covered all the holes when I removed the intake so nothing falls in the engine. Before starting the work, I also vacuumed the top of the engine to remove any debris. When I put everything back together and started the engine, there was this very loud knock. It sounded like something loose inside the engine. I then got the P0301 code. I stopped the engine and took everything apart again. It was much faster the second time. I rechecked everything to see if I missed anything. Everything checked fine. Thinking the Denso spark plugs may be bad, I switched to new NGK 4589 spark plugs. I also replaced all 3 bank 1 COPs with Denso COPs. I put everything back together with new felpro gaskets and restarted the van. I heard loud knocking sound (sounds like something g rattling inside) and got p0301 again. Can someone please help me find out what’s wrong? I am sure nothing fell inside the engine because I covered all the exposed holes and used all bolts, nuts and washers that I took off.
 

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If it was a simple misfire/rough running, I'd suspect a vacuum leak or a bad coil or, more likely a not seated or not grounded coil. However, a loud knocking indicates either something fell in the engine, despite all your precautions or you have a cylinder compression issue which is causing poor combustion and detonation. The possibility I could think of is that a plug crush washer stayed down in the hole and now you have two of them in there, giving you a compression leak. If something fell in, the only hope is that you can snake a camera down there and see it and then somehow remove it, but I have no idea how you'd actually accomplish that. Other than that, the third possibility I could think of is something I'm not sure is possible. If you accidentally switched the wiring around (swapped two cylinders?), you may have totally changed the firing order. I've never done a plug change on the Sienna, but most cars with individual coil packs have wiring that can only reach one place, but it might be possible to reverse two of them.
 

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Is the knock random in nature like pop corn popping OR is it rhythmical? Are the knock sensor harness new? Is the spark plug you removed from cylinder 1 damaged?
 

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Discussion Starter · #4 ·
Is the knock random in nature like pop corn popping OR is it rhythmical? Are the knock sensor harness new? Is the spark plug you removed from cylinder 1 damaged?
Is the knock random in nature like pop corn popping OR is it rhythmical? Are the knock sensor harness new? Is the spark plug you removed from cylinder 1 damaged?
Oh crap! I didn’t even think that a washer could have been left behind. The knock sensor harness is new. The spark plug that I removed from cylinder 1 is not damaged. The sound is totally random. So it sounds like I’m gonna have to remove the cylinder to see if anything on top of the piston.
 

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Oh crap! I didn’t even think that a washer could have been left behind.
Though possible , it is hardly likely. But if indeed that washer was left behind I think the knocking would sound like an explosive one due to the new plug not seating properly, perhaps? , rather than a "mechanical " one. I also believe the washer is larger than the plug hole so I doubt it fell into the plug hole and into the cylinder. Look at the number one plug you removed , is the washer on it or no? If you are not sure which was number one plug look at all of them for a missing washer. Since the sound is random " something" is in that cylinder. It might be in cylinder one BUT it could be others as well , the code for number one misfire might not necessarily mean the "object" is in cylinder one. By the way , you are not the only one to have experienced this. Another member experienced the same issue but have not posted back , to the best of my knowledge , as to what was discovered. It must be frustrating for you.
 

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Discussion Starter · #6 ·
Though possible , it is hardly likely. But if indeed that washer was left behind I think the knocking would sound like an explosive one due to the new plug not seating properly, perhaps? , rather than a "mechanical " one. I also believe the washer is larger than the plug hole so I doubt it fell into the plug hole and into the cylinder. Look at the number one plug you removed , is the washer on it or no? If you are not sure which was number one plug look at all of them for a missing washer. Since the sound is random " something" is in that cylinder. It might be in cylinder one BUT it could be others as well , the code for number one misfire might not necessarily mean the "object" is in cylinder one. By the way , you are not the only one to have experienced this. Another member experienced the same issue but have not posted back , to the best of my knowledge , as to what was discovered. It must be frustrating for you.
I have the mind to tear everything apart again but I don’t know what I’d do next. It could very well be that something fell in there that I don’t know about. I’ve never worked on anything on top of the engine. The only things that I’ve done is brake work, and replaced the rack and pinion. I have had the spark plugs replaced at 120k miles (215k miles now) and timing belt/water pump changed twice by my local garage. Taking the heads off is beyond my abilities so I guess I’d just get it towed to my local garage again and have to them look at it. Hopefully, the sienna can still be saved.
 

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Discussion Starter · #7 ·
I have the mind to tear everything apart again but I don’t know what I’d do next. It could very well be that something fell in there that I don’t know about. I’ve never worked on anything on top of the engine. The only things that I’ve done is brake work, and replaced the rack and pinion. I have had the spark plugs replaced at 120k miles (215k miles now) and timing belt/water pump changed twice by my local garage. Taking the heads off is beyond my abilities so I guess I’d just get it towed to my local garage again and have to them look at it. Hopefully, the sienna can still be saved.
Do you happen to remember what the other member wrote so I could search for it?
 

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The other member did not provide closure and I tried reaching out to no avail. One possible thing you could try is to get a camera ( like a boroscope one , from amazon ) and peek into the cylinders preferably at top dead center ( rotate crank with hand ) to see if there is something causing the knock. I thought about something falling in when the plugs were removed but that is hardly likely too since the plug seals prevent ingress of dirt. BUT if that were the case and that object is holding a valve open the I suspect the sound would be rhythmical rather than mechanical and random. Could the sound be external? This is a tough one as you don't necessarily want to run the engine for any length of time causing more internal damage if that be the case. Before you give it to a tech it might be worth your while to get a camera and investigate yourself , since you know by now how to remove things. A telescopic magnet would be handy to remove any metal object from the cylinders. I take it when you buttoned things up that all nuts and washers were accounted for? Were any of the intake gaskets broken when you removed them? Im thinking of the possibility of a piece falling in unnoticed. Then again when I did mine those gaskets are pretty tough.
 

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Discussion Starter · #9 ·
The other member did not provide closure and I tried reaching out to no avail. One possible thing you could try is to get a camera ( like a boroscope one , from amazon ) and peek into the cylinders preferably at top dead center ( rotate crank with hand ) to see if there is something causing the knock. I thought about something falling in when the plugs were removed but that is hardly likely too since the plug seals prevent ingress of dirt. BUT if that were the case and that object is holding a valve open the I suspect the sound would be rhythmical rather than mechanical and random. Could the sound be external? This is a tough one as you don't necessarily want to run the engine for any length of time causing more internal damage if that be the case. Before you give it to a tech it might be worth your while to get a camera and investigate yourself , since you know by now how to remove things. A telescopic magnet would be handy to remove any metal object from the cylinders. I take it when you buttoned things up that all nuts and washers were accounted for? Were any of the intake gaskets broken when you removed them? Im thinking of the possibility of a piece falling in unnoticed. Then again when I did mine those gaskets are pretty tough.
I made sure to separate the bolts, nuts and washers by component so that I don’t mix them up. When I was done, all of them were accounted for. I still have the old intake manifold metal gasket. Some of the rubber surrounding the holes came off but they came off in one piece so I’m pretty sure those didn’t fall in.
 

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Well , I am curious to see what could be causing this knocking. The p0301 is troubling.
 

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Great! I'll be here.
BTW..you did tighten those knock sensor. Yes?
 

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Discussion Starter · #13 ·
Yes I tightened the knock sensors. My van was parked in the driveway when I worked on it. When the intake manifold was removed , I just swung it upside down to the side of the battery because I didn’t disconnect the fuel rails.
 

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Discussion Starter · #14 ·
Yes I tightened the knock sensors. My van was parked in the driveway when I worked on it. When the intake manifold was removed , I just swung it upside down to the side of the battery because I didn’t disconnect the fuel rails.
Would a loose knock sensor cause the random rattle?
 

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Was away for the long weekend, so I didn't contribute further. Reading through this, I'm a little confused/uncertain and it might be creating red herrings. Random rattle and engine knock are two totally different things.

Knocking in the top end could be mechanical (something in a cylinder, a stuck valve, off timing, etc.) with metal hitting metal. This is a worst-case scenario. I would expect this to be rhythmic (clank-clank-clank-clank) or maybe sinusoidal (quiet-quiet-tap-tap-clank-clank-thunk-clank-clank-tap-tap-quiet-quiet). Even if no metal fell into the engine when working on things, there's always the possibility of a chunk of carbon build-up getting in there.

Knocking could ALSO be caused by detonation. The ACTUAL purpose of the knock sensor is to stop this from causing damage. Detonation could be caused by a too-lean or too-rich condition or a lack of compression. This last reason was the reason I suggested the possibility of the washer from the spark plug being left behind. If you have the old plugs and they all still have the washers on them, you can safely rule this possibility out. The only other thing which might cause poor compression would be if you cross-threaded a plug or didn't tighten it down to crush the crush washer. But if you threaded them in finger-tight first and then tightened them properly, those options can also be ruled out. So, that leaves a too-rich or too-lean option. Too rich can probably be ruled out, assuming you didn't so something like spray TB cleaner into anything or short out a fuel injector wire. But, if any of the gaskets on the intake side of things isn't an ideal match or was one of those cut-to-fit types, you might have an intake obstruction, causing a rich condition. So, that leaves too lean as an option. Too lean is a highly suspect condition, given the scope of the work and the impact on the intake system. Any vacuum leaks could cause a misfire. If you damaged the intake boot (not uncommon on a 16 year-old vehicle) or didn't properly seat/torque everything, you could be sucking substantial air into the system causing poor combustion and misfiring which could be totally random. The one other thing you should carefully check would be the knock sensor harness. If the knock sensor were malfunctioning and it retards the timing, that could produce a misfire, but if I recall correctly, I think you have to take everything apart again to check this, which kinda sucks.

A few other things that could be an issue... Incorrect torque on any bolts in the intake system, an ungrounded coil, a damaged coil (one that you didn't replace), swapping the wires on two coils which changes the firing order (as I said originally, I'm not sure if that's actually possible), accidental damage to something unrelated (i.e. injector rail, throttle body, etc.), a cable that was left disconnected and is causing the engine to run in "default" settings mode, an ECU which defaulted back to the standard fuel maps in a 16 year-old vehicle which is producing poor combustion and needs to re-learn all the fuel maps and trims or, unfortunately, something totally unrelated that might just have manifested coincidentally (unlikely) but does happen. My rear wheel speed sensor crapped out 2 days after I had a bunch of exhaust work and a safety/emissions inspection done.
 

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Discussion Starter · #16 ·
I decided to take the car to my mechanic and this is what he found. He scoped the #1 cylinder and found a piece of metal in there. He said it doesn’t look like a bolt or nut. All the nuts, bolts and washers I removed were accounted for. Mechanic said there was a lot of carbon buildup in cylinder and what looks like damage to cylinder wall. This has basically turned into a head gasket type job and was quoted at least $1500 if no other problems are found. My van has 215k miles so I’m leaning towards not fixing this anymore and just getting rid of it. I’ve put a lot of work in this van but I am afraid this is just the beginning. Thanks to everyone for the help and advice.
 

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I decided to take the car to my mechanic and this is what he found. He scoped the #1 cylinder and found a piece of metal in there. He said it doesn’t look like a bolt or nut. All the nuts, bolts and washers I removed were accounted for. Mechanic said there was a lot of carbon buildup in cylinder and what looks like damage to cylinder wall. This has basically turned into a head gasket type job and was quoted at least $1500 if no other problems are found. My van has 215k miles so I’m leaning towards not fixing this anymore and just getting rid of it. I’ve put a lot of work in this van but I am afraid this is just the beginning. Thanks to everyone for the help and advice.
That stinks! Although, if you're a reasonably proficient DIYer, you and a couple car buddies could throw a used engine in there for about the same price. You could put the new plugs and coils out of the old engine, do a timing belt/water pump, and all the other hard-to-do jobs with the engine out of the car and then drop it into the van. OR you could just ask the mechanic to try to fish the metal out of there, inspect the threads from the plug hole (common source of random metal in a cylinder) and run the van for another 30k miles, with the understanding that it may run a little rough and/or burn a little oil. OR you could look for a newer Gen2 Sienna, because, as we all know, the Gen2 Siennas are really the best vans out there.
 

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Was the mechanic able to get the piece of metal out of the cylinder?

Good luck, whichever direction you take.
 
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