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Old 10-26-2014, 11:06 PM
wtrskr wtrskr is offline
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Fogging TBI - Oil not reaching #1 cylinder

When I fog through the throttle body with Marvel Mystery Oil, the oil seems to reach all but one of the cylinders. I know this because I check the plugs after shutting down the engine. Only one is dry. This is the second straight year I noticed this happening, and it has been the same cylinder both years (passenger side, closest to bow).

Should I worry about this? Does this mean gas likely isn't reaching that cylinder?

The ECM isn't throwing any error codes.
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Old 10-27-2014, 12:30 AM
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I would not worry about it too much.. just food thru the plug hole for piece of mind.
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Old 10-27-2014, 07:31 PM
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Originally Posted by mikeg205 View Post
I would not worry about it too much.. just food thru the plug hole for piece of mind.
Just to clarify, I'm not worried about it from a winterizing perspective. I did fog through the plug hole instead. I'm worried that my intake valve is not opening properly, or I have a blockage passage, or something of the like.

If the fogging oil doesn't find its way to that cylinder, couldn't that mean gas isn't making it there either?

thx
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Old 10-27-2014, 08:22 PM
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The injectors spray and atomize the fuel into a nice cone shape for even distribution between cylinders. Spraying and or pouring MM oil is not the same. If fuel wasn't reaching # 1 cylinder you would know.
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Old 10-27-2014, 08:28 PM
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Originally Posted by wtrskr View Post
When I fog through the throttle body with Marvel Mystery Oil, the oil seems to reach all but one of the cylinders. I know this because I check the plugs after shutting down the engine. Only one is dry. This is the second straight year I noticed this happening, and it has been the same cylinder both years (passenger side, closest to bow).

Should I worry about this? Does this mean gas likely isn't reaching that cylinder?

The ECM isn't throwing any error codes.
#1, at the crank end of the engine? Do a vacuum test and if possible, leak-down, too.

Is the PCV hose connected to a cylinder runner, or the base of the throttle body? If it's connected to the runner, move it to the base of the throttle body (in the spacer). That cylinder can run lean because the PCV valve acts like a semi-controlled vacuum leak. You can test this by plugging the hose and trying to fog it- if it gets oil into the dry cylinder, you know what to do.

Pouring oil into the intake isn't a great way to fog- it's trying to drag the oil uphill. Better to use something that has lower viscosity.
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Old 10-27-2014, 08:29 PM
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It would be missing while running if it wasnt getting gas. Especially during acceleration. My thought would be that for some reason pouring through the throttle body maybe that cylinder is the furtherest away???? Or just a coincidence, maybe it has something to do with it being the first to pull it in, and after iy goes through all the other cylinders it kills the engine and doesnt get a chance to pull anymore in???? I agree that it is odd, but if that intake valve wasnt doing its job you would definitely know it
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Old 10-27-2014, 09:06 PM
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Originally Posted by paco_06 View Post
It would be missing while running if it wasnt getting gas. Especially during acceleration. My thought would be that for some reason pouring through the throttle body maybe that cylinder is the furtherest away???? Or just a coincidence, maybe it has something to do with it being the first to pull it in, and after iy goes through all the other cylinders it kills the engine and doesnt get a chance to pull anymore in???? I agree that it is odd, but if that intake valve wasnt doing its job you would definitely know it
It might miss, but it wouldn't necessarily be noticeable.
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Old 10-27-2014, 10:13 PM
wtrskr wtrskr is offline
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Originally Posted by JimN View Post
#1, at the crank end of the engine? Do a vacuum test and if possible, leak-down, too.

Is the PCV hose connected to a cylinder runner, or the base of the throttle body? If it's connected to the runner, move it to the base of the throttle body (in the spacer). That cylinder can run lean because the PCV valve acts like a semi-controlled vacuum leak. You can test this by plugging the hose and trying to fog it- if it gets oil into the dry cylinder, you know what to do.

Pouring oil into the intake isn't a great way to fog- it's trying to drag the oil uphill. Better to use something that has lower viscosity.
Yes, it is the #1 at the crank end of the engine. The PCV hose goes from the flame arrestor to the valve cover on that side (passenger side). There is a separate vacuum hose from the Throttle body to the Map sensor.

A couple of years ago I had some issues and had done a compression test and a vacuum test. They both tested out well, though that could have changed since then. I've never done a leak down.

To tell you the truth I'm leaning toward dealing with this in the Spring because the battery is out and everything is ready to go for the winter. My garage could also start getting pretty cold for doing wrench work. Good to know it is something to look further into and, at the same time, there could be a reason the oil didn't get to that cylinder the last two times I winterized (#1 can run lean).

Is it possible that using Sea Foam or something like that could clear things out if there is blockage?

Thanks for the tip on fogging.
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Old 10-28-2014, 06:45 AM
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Originally Posted by wtrskr View Post
Yes, it is the #1 at the crank end of the engine. The PCV hose goes from the flame arrestor to the valve cover on that side (passenger side). There is a separate vacuum hose from the Throttle body to the Map sensor.

A couple of years ago I had some issues and had done a compression test and a vacuum test. They both tested out well, though that could have changed since then. I've never done a leak down.

To tell you the truth I'm leaning toward dealing with this in the Spring because the battery is out and everything is ready to go for the winter. My garage could also start getting pretty cold for doing wrench work. Good to know it is something to look further into and, at the same time, there could be a reason the oil didn't get to that cylinder the last two times I winterized (#1 can run lean).

Is it possible that using Sea Foam or something like that could clear things out if there is blockage?

Thanks for the tip on fogging.
I would think about buying a spray can of fogging oil and pull the #1 plug, so that cylinder can be fogged. This would require re-connecting the battery and cranking the engine.

I don't remember Marvel Mystery Oil being particularly thin, which would seem to be causing the problem. Since gas has such low viscosity, it atomizes very easily and besides, the fumes are combustible, so it will still ignite and create power but thick oil won't make it to the cylinder if it has to go uphill. The angle of the engine makes a big difference, too. If you could position the boat so the engine is level when you do this in the future, the problem might disappear.
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Old 10-28-2014, 07:57 AM
wtrskr wtrskr is offline
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It is just interesting to me that the oil made it to all the other cylinders and two years in a row.

I'm wondering if I might be able to tell if anything is wrong by taking off that valve cover and spinning the engine by hand? Might I be able to see if that valve is lifting in the same fashion as the others?
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