Power Valve Screw Failure

[Jb510]

So I pulled the upper plenum yesterday to locktite the power valve screws and found 2 missing butterflies and 4 missing screws that held them in. Was able to fish one butterfly out of the cylinder with a magnet but can’t find the other butterfly or any screws.

Going to remove lower plenum today just need to grab a deeper socket for one of the bolts. I can’t even find a used butterfly valve without getting the whole lower intake manifold collector which is $750 used. Might get lucky if the last valve is still in there and the 4 screws passed without getting stuck or scoring anything inside.

It runs and idles smooth but probably burns way more gas by giving extra air and power to the engine when it doesn’t call for it, can’t think of anything else bad that could happen though. This is my first go at an engine repair, never even changed an oil filter, everything went smooth till I found missing parts fml!

[Jb510]

This a new to me vehicle, 2004 SE with 99k miles on it.

[The Grand Pooh-Bah]

Wow that really sucks. I would get a scope and do some inspecting around the valves.

I pulled mine today to perform a bunch of maintenance, including loctite on the intake screws. Everything was intact on mine with 165k miles.

[mdmellott]

You'll find the other valve plate when you remove the lower plenum for sure. There's no way it got past the swirl valves in the intake manifold. Those tiny screws are another matter. Forum member rgk has experience dealing with that. 3-5l-vq35de-overhaul-t626269.html
Those screws can pass through the intake valves into the cylinder. I'm not sure they can pass back out through the exhaust valves without getting pulverized first. In rgk's case, his piston crowns and cylinder head took a beating in the process. rgk posted some great pictures and a write up of all this in the link above. With any luck, you'll find those screws too, sitting in the lower plenum or in the intake port of the head.

[Jb510]

Just bought a scope on amazon being delivered today

[Jb510]

You'll find the other valve plate when you remove the lower plenum for sure. There's no way it got past the swirl valves in the intake manifold. Those tiny screws are another matter. Forum member rgk has experience dealing with that. 3-5l-vq35de-overhaul-t626269.html
Those screws can pass through the intake valves into the cylinder. I'm not sure they can pass back out through the exhaust valves without getting pulverized first. In rgk's case, his piston crowns and cylinder head took a beating in the process. rgk posted some great pictures and a write up of all this in the link above. With any luck, you'll find those screws too, sitting in the lower plenum or in the intake port of the head.

I hope so, thanks for the link, thought I already read everything online about it.

The things he did removing the engine out are way beyond my capabilities but it’s good to know what the end all be all solution is. Actually not sure if it’s good lol.

[Jb510]

You'll find the other valve plate when you remove the lower plenum for sure. There's no way it got past the swirl valves in the intake manifold. Those tiny screws are another matter. Forum member rgk has experience dealing with that. 3-5l-vq35de-overhaul-t626269.html
Those screws can pass through the intake valves into the cylinder. I'm not sure they can pass back out through the exhaust valves without getting pulverized first. In rgk's case, his piston crowns and cylinder head took a beating in the process. rgk posted some great pictures and a write up of all this in the link above. With any luck, you'll find those screws too, sitting in the lower plenum or in the intake port of the head.

I hope so, thanks for the link, thought I already read everything online about it.

The things he did removing the engine out are way beyond my capabilities but it’s good to know what the end all be all solution is. Actually not sure if it’s good lol.

[Jb510]

You'll find the other valve plate when you remove the lower plenum for sure. There's no way it got past the swirl valves in the intake manifold. Those tiny screws are another matter. Forum member rgk has experience dealing with that. 3-5l-vq35de-overhaul-t626269.html
Those screws can pass through the intake valves into the cylinder. I'm not sure they can pass back out through the exhaust valves without getting pulverized first. In rgk's case, his piston crowns and cylinder head took a beating in the process. rgk posted some great pictures and a write up of all this in the link above. With any luck, you'll find those screws too, sitting in the lower plenum or in the intake port of the head.

I used a pretty long flexible magnet to get, what felt like, all the way into the cylinder where I fished one of the butterflies out of. Do you think the screws would really be there once I remove lower plenum? Are there hiding spots in there the magnet wouldn’t get to?

[mdmellott]

Through the lower plenum, you are able to fish all the way to the intake manifold, maybe even past the swirl control valve plates in the manifold and into the cylinder head intake port but not into the cylinders themselves. When you remove the lower plenum you will be able to see the swirl control valves and the back side of the intake valves. There is no place at that stage of disassembly for the screws to hide. Odds are not favorable that those screws are just sitting there but it's possible I suppose.

[Jb510]

Through the lower plenum, you are able to fish all the way to the intake manifold, maybe even past the swirl control valve plates in the manifold and into the cylinder head intake port but not into the cylinders themselves. When you remove the lower plenum you will be able to see the swirl control valves and the back side of the intake valves. There is no place at that stage of disassembly for the screws to hide. Odds are not favorable that those screws are just sitting there but it's possible I suppose.

So if I were to not find any screws but find the last butterfly, screw all butterflies back in and locktite screws, would I be good moving forward and in the clear? If the damage was done, would I tell right away, or the damage might lead to problems in the future?

I appreciate all your help

[mdmellott]

If it was mine and I couldn't find the screws, I would put it all back together with new screws and Loctite and hope for the best. You mentioned that your engine runs and idles smooth so that's good news. I don't know if there would be any issues down the road if damage was done but nothing consequential has happened right away. In either case, whether you find the screws or not, keep hope alive.

[VStar650CL]

If it was mine and I couldn't find the screws, I would put it all back together with new screws and Loctite and hope for the best. You mentioned that your engine runs and idles smooth so that's good news. I don't know if there would be any issues down the road if damage was done but nothing consequential has happened right away. In either case, whether you find the screws or not, keep hope alive.

+1. It's always possible with small parts that they bounced through the intake valve and out the exhaust, and now they're keeping your catalyst company. Chances are they dinged some stuff on the way through, but if your compression didn't suffer then you may be in the clear. If you want to be certain, the best course is to remove the plenum and the plugs and make yourself a bendable fishing-magnet with Gray Death and a coathanger. Fish the lower perimeter of the cylinders and the backs of the intake valves (it's possible for carbon buildup to keep a screw from passing an intake valve).

[Jb510]

If it was mine and I couldn't find the screws, I would put it all back together with new screws and Loctite and hope for the best. You mentioned that your engine runs and idles smooth so that's good news. I don't know if there would be any issues down the road if damage was done but nothing consequential has happened right away. In either case, whether you find the screws or not, keep hope alive.

That’s what I’m going to do, I was just concerned about the longevity of the car, just bought it 2 weeks ago and with 99k miles, I was hoping to get at least 100k out of it, being a second vehicle was also planning to have it for many years.

[Jb510]

If it was mine and I couldn't find the screws, I would put it all back together with new screws and Loctite and hope for the best. You mentioned that your engine runs and idles smooth so that's good news. I don't know if there would be any issues down the road if damage was done but nothing consequential has happened right away. In either case, whether you find the screws or not, keep hope alive.

+1. It's always possible with small parts that they bounced through the intake valve and out the exhaust, and now they're keeping your catalyst company. Chances are they dinged some stuff on the way through, but if your compression didn't suffer then you may be in the clear. If you want to be certain, the best course is to remove the plenum and the plugs and make yourself a bendable fishing-magnet with Gray Death and a coathanger. Fish the lower perimeter of the cylinders and the backs of the intake valves (it's possible for carbon buildup to keep a screw from passing an intake valve).

Thanks for the info, I could do a compression test I read to check for a few things, but it is running smooth. I will remove the lower plenum when the deep socket gets delivered soon. I’ve never taken apart anything in an engine prior to this (37 yrs old) and I wanted to change spark plugs because I read it’s right there but I’d have to do a bunch of research on setting the measurements because that was confusing at first. Sure a YouTube video would solve it but not sure about any tools needed. I do have a automotive magnet with a bendable long 24 inch wire bendable pole, that’s how I fished the 1 butterfly out. It stopped about 8 or 10 inches in and didn’t pull anything out. Would removing the plugs be more important than removing just the lower plenum?

[VStar650CL]

Sure, you want to fish inside the cylinders too. Depending on the geometry of the combustion chamber, It's possible for a squashed or chewed-up screw to kick around in there and gradually do damage to the walls. You're best off checking every place that's checkable.

[Jb510]

Sure, you want to fish inside the cylinders too. Depending on the geometry of the combustion chamber, It's possible for a squashed or chewed-up screw to kick around in there and gradually do damage to the walls. You're best off checking every place that's checkable.

These are two cylinders with just the upper plenum off, using a borescope I just got.

[Jb510]

Man I’m stuck, can’t get to this bolt to remove the non bendable rubber hose that’s the last piece to removing the lower plenum, it’s not just 4 bolts.

[Jb510]

Pic of bolt

[Jb510]

Can anyone tell me if it’s bad if I put everything back together and am missing 1 butterfly? Is it just bad gas mileage?

Using a borescope I was stopped at the picture above, and don’t think removing the lower plenum anyways would give me more access to what I can see with the camera, which there is no last butterfly in there like the one I fished out.

The lower intake manifold collector is 750 used on eBay and I can’t find just the butterfly to replace.

[VStar650CL]

You may get misfiring if just one butterfly is MIA. It will run without any butterflies at the cost of some mileage, that's probably a better option if you can't replace it. I'd check the JY and see if they have a used junker that's headed for the crusher.

[mdmellott]

Pic of bolt

That bolt location design is very awkward. A 12 point closed wrench is your best tool choice for this. I spent more time on this one bolt then I did on every other bolt for the upper and lower plenums combined. Since you cannot see it at the same time you are applying the wrench to it, the patience needed is a challenge. I found it easier to get a wrench on it if I just closed my eyes, seriously.

[mdmellott]

Can anyone tell me if it’s bad if I put everything back together and am missing 1 butterfly? Is it just bad gas mileage?

Using a borescope I was stopped at the picture above, and don’t think removing the lower plenum anyways would give me more access to what I can see with the camera, which there is no last butterfly in there like the one I fished out.

The lower intake manifold collector is 750 used on eBay and I can’t find just the butterfly to replace.

It's a bad idea to put it back together with the missing butterfly stuck in there somewhere. It is not possible for it to have fallen off and not be in there unless it was previously removed when all of this was last dismantled. Your engine intakes are so clean, like new, it is likely this was addressed once before and cleaned up at the same time. If you are 100% confident you have seen all there is to see with your bore scope and that the butterfly is not in there, then put it back together. Looking at the back side of your intake valve is as far as you can possibly go.

Remove all of your butterfly valve plates and reinstall them with Loctite. This might be also be a challenge if any of those tiny screws had Loctite previously applied. (Obviously, not the ones that fell off.) A heavy duty soldering iron used to heat up the screws will free up any previous thread locker that was applied.

[Jb510]

You may get misfiring if just one butterfly is MIA. It will run without any butterflies at the cost of some mileage, that's probably a better option if you can't replace it. I'd check the JY and see if they have a used junker that's headed for the crusher.

I’ve been running with 2 butterflies missing for about 400 miles since I’ve purchased the car an no check engine lights or codes thrown. Was able to find part numbers for the power valve plate and pin dowel, what Nissan calls the screws, for an Altima with same problem, and they looked identical so should be here tomorrow. My only concern at this point is the butterfly valve I can’t find.

[VStar650CL]

Looking at the back side of your intake valve is as far as you can possibly go.

Since the OP has a borescope, I'd pull the plugs and scope the cylinders too, for both the missing screw and the butterfly. I'm sure a butterfly can't get past the intake valve in one piece, but it's a lightweight part and I wouldn't exclude the notion that it could fold up or get bent into a Pringle.

[Jb510]

Pic of bolt

That bolt location design is very awkward. A 12 point closed wrench is your best tool choice for this. I spent more time on this one bolt then I did on every other bolt for the upper and lower plenums combined. Since you cannot see it at the same time you are applying the wrench to it, the patience needed is a challenge. I found it easier to get a wrench on it if I just closed my eyes, seriously.

Yea I can feel it more than I am see. I’m short too so makes it even harder. Thanks for the 12 point tip, was using 6. I just can’t get my hand in the space between the bolt and firewall at the low enough angle to twist the bolt free. Did you come at it from the front left or right side. I’ve been trying from the passenger side mostly.

[Jb510]

I found the parts at my local dealer and will get them tomorrow.

I am confident I’m hitting the end of each cylinder without seeing the plate. Only the upper plenum is removed currently. It makes sense it should be there so I will check again all the cylinders, even ones that still have their plates.

I didn’t see any locktite on and power valve screws.

Can anyone tell me if it’s bad if I put everything back together and am missing 1 butterfly? Is it just bad gas mileage?

Using a borescope I was stopped at the picture above, and don’t think removing the lower plenum anyways would give me more access to what I can see with the camera, which there is no last butterfly in there like the one I fished out.

The lower intake manifold collector is 750 used on eBay and I can’t find just the butterfly to replace.

It's a bad idea to put it back together with the missing butterfly stuck in there somewhere. It is not possible for it to have fallen off and not be in there unless it was previously removed when all of this was last dismantled. Your engine intakes are so clean, like new, it is likely this was addressed once before and cleaned up at the same time. If you are 100% confident you have seen all there is to see with your bore scope and that the butterfly is not in there, then put it back together. Looking at the back side of your intake valve is as far as you can possibly go.

Remove all of your butterfly valve plates and reinstall them with Loctite. This might be also be a challenge if any of those tiny screws had Loctite previously applied. (Obviously, not the ones that fell off.) A heavy duty soldering iron used to heat up the screws will free up any previous thread locker that was applied.

[Jb510]

Looking at the back side of your intake valve is as far as you can possibly go.

Since the OP has a borescope, I'd pull the plugs and scope the cylinders too, for both the missing screw and the butterfly. I'm sure a butterfly can't get past the intake valve in one piece, but it's a lightweight part and I wouldn't exclude the notion that it could fold up or get bent into a Pringle.

No prior mechanical engine experience before this and was a little overwhelmed with spark plug change but did some research and I really should do this step. Just don’t know where to begin on the pathfinder as the videos I watched were different vehicles.

[VStar650CL]

Not much to removing the plugs once the plenum is off, just be careful to keep the socket straight so you don't crack any insulators. There shouldn't be any need to hand-spin the engine to get a look with the scope unless one of them happens to be dead on TDC. There's actually a pretty fair chance you'll find your missing screw embedded in the top of a piston, I've seen it several times. If so, and if a magnet won't pull it loose, just leave it there. I know of several cases both personally and online where people drove the car for the rest of its life that way with no issues. My suspicion is that the differential metals actually bond together at the high temperatures in the cylinder and prevent it ever coming out.

[Jb510]

That’s where you lose me lol need to do more research

“There shouldn't be any need to hand-spin the engine to get a look with the scope unless one of them happens to be dead on TDC.”

From what I understand though, it seems better chance I’ll find missing parts by pulling the spark plugs, than I would by pulling the whole lower plenum??

Not much to removing the plugs once the plenum is off, just be careful to keep the socket straight so you don't crack any insulators. There shouldn't be any need to hand-spin the engine to get a look with the scope unless one of them happens to be dead on TDC. There's actually a pretty fair chance you'll find your missing screw embedded in the top of a piston, I've seen it several times. If so, and if a magnet won't pull it loose, just leave it there. I know of several cases both personally and online where people drove the car for the rest of its life that way with no issues. My suspicion is that the differential metals actually bond together at the high temperatures in the cylinder and prevent it ever coming out.

[Jb510]

Where will I find the top of a piston? Once I remove the spark plug?

Not much to removing the plugs once the plenum is off, just be careful to keep the socket straight so you don't crack any insulators. There shouldn't be any need to hand-spin the engine to get a look with the scope unless one of them happens to be dead on TDC. There's actually a pretty fair chance you'll find your missing screw embedded in the top of a piston, I've seen it several times. If so, and if a magnet won't pull it loose, just leave it there. I know of several cases both personally and online where people drove the car for the rest of its life that way with no issues. My suspicion is that the differential metals actually bond together at the high temperatures in the cylinder and prevent it ever coming out.