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Old 12-07-2018, 08:33 PM   #1
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2009 Ford F150 engine misfiring


Have had two sets of coilpacks replaced on my 4.6 liter F150.

Mechanic found the #8 spark plug covered in oil from top to bottom.

These plugs go into the engine from the top by the intake manifold with the coilpack on top not underneath the valve covers like I grew up with.

Mechanic said it didn't take much to loosen this spark plug but it was more than fingertight. He suggested an intake manifold leak but I never heard of oil inside an intake manifold. Cooling fluid maybe but oil? My theory is the piston's oil rings might be going (248,000) but could the piston compression push the oil past the threads then up into the coilpack?


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Old 12-07-2018, 08:48 PM   #2
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Re: 2009 Ford F150 engine misfiring


I would drive it with a new tight spark plug for a while and see if that helped, if not do the compression test. If that passes then think about valve stem seals leaking oil from the head. You can change those by adding air pressure to the cylinder to hold the valves closed.
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Old 12-08-2018, 11:26 AM   #3
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Re: 2009 Ford F150 engine misfiring


Yup, I agree with Neal. At a quarter of a million miles it seems perfectly logical to me that the engine is using at least some oil. And the only logical explanation for the top part of the spark plug to be soaked, again, to me anyway, is because it was escaping past the loose plug. Either that or you have a leaking valve cover gasket or whatever, but you should see more evidence than just around the plug. My guess is that it has been using some extra oil for some time now, maybe for the past 100,000 miles or so, not necessarily a lot, but some, and that the engine was simply burning it. Then the loose plug came into the mix and it was easier for the engine to just push some of it out than to burn all of it.
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Old 12-08-2018, 11:35 AM   #4
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Re: 2009 Ford F150 engine misfiring


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Yup, I agree with Neal. At a quarter of a million miles it seems perfectly logical to me that the engine is using at least some oil. And the only logical explanation for the top part of the spark plug to be soaked, again, to me anyway, is because it was escaping past the loose plug. Either that or you have a leaking valve cover gasket or whatever, but you should see more evidence than just around the plug. My guess is that it has been using some extra oil for some time now, maybe for the past 100,000 miles or so, not necessarily a lot, but some, and that the engine was simply burning it. Then the loose plug came into the mix and it was easier for the engine to just push some of it out than to burn all of it.
It is the valve stem seal, I would be looking at.
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Old 12-08-2018, 11:42 AM   #5
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Re: 2009 Ford F150 engine misfiring


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Old 12-08-2018, 01:40 PM   #6
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Re: 2009 Ford F150 engine misfiring


Due to the facts that I can't remember a lot of things any more and haven't been able to keep up with a lot of the innovations of recent years, I confess to not being half as good as I used to be under the hood. Nevertheless, I do know what you mean Neal, and it seems 100% plausible, particularly with that many miles on the vehicle. But it doesn't make sense to me that worn valve stem seals would contribute directly to oil accumulating around the external part of the spark plug; that would be due, I think, to the spark plug not being fully tightened. So my point is that, now that the spark plug has been replaced and properly tightened, I would drive it for a bit, at least a few days, and see how it runs. After that, given the circumstances, yes, I would do a compression test on all of the cylinders, just as you said earlier. That's what I was agreeing with. After that, for me anyway, it would be a matter of deciding if I wanted to put any more dollars in it or start looking for another vehicle. Not that I would necessarily get rid of a vehicle over valve stem seals alone, but I don't know what kind of shape the rest of the vehicle is.
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Old 12-08-2018, 01:48 PM   #7
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Re: 2009 Ford F150 engine misfiring


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Originally Posted by DexterII View Post
Due to the facts that I can't remember a lot of things any more and haven't been able to keep up with a lot of the innovations of recent years, I confess to not being half as good as I used to be under the hood. Nevertheless, I do know what you mean Neal, and it seems 100% plausible, particularly with that many miles on the vehicle. But it doesn't make sense to me that worn valve stem seals would contribute directly to oil accumulating around the external part of the spark plug; that would be due, I think, to the spark plug not being fully tightened. So my point is that, now that the spark plug has been replaced and properly tightened, I would drive it for a bit, at least a few days, and see how it runs. After that, given the circumstances, yes, I would do a compression test on all of the cylinders, just as you said earlier. That's what I was agreeing with. After that, for me anyway, it would be a matter of deciding if I wanted to put any more dollars in it or start looking for another vehicle. Not that I would necessarily get rid of a vehicle over valve stem seals alone, but I don't know what kind of shape the rest of the vehicle is.
The spark plug was not tight enough and compression is pushing it out around the spark plug. If the oil was an external leak the plug would not be fouled inside the chamber.
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Old 12-08-2018, 02:20 PM   #8
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Re: 2009 Ford F150 engine misfiring


See this is all part of that "can't remember things any more" thing. And believe me, I'm not being argumentative at all, just finishing the thoughts I had but forgot to mention. Maybe the valve stem seals are indeed worn, and, as I said before, this seems completely plausible given the mileage. Are they worn enough to be a problem, or are they maybe at what one would call normal or even just marginal. Now toss in a loose spark plug, and what exactly does that do? Could it exacerbate the situation? Could it affect the combustion characteristics such as flow and temperature enough to cause excess oil to accumulate? Could a perfectly acceptable amount of oil getting past the valve stem seals become a problem under this condition? Again, not at all being argumentative because I don't know, particularly with only the information that has been provided, but these are the reason that, given what we have, I would run it, see if things have improved with the new plug, run a compression check once things have had a chance to settle, and see how it shakes out from there. Oh, and I would also hook up my OBD reader, or stop by the local auto parts store OP, most of which will run afree scan for you, and see what it shows. And, depending on what they are, I would most likely clear any related codes because the computer could still be trying to compensate for a problem that has already been resolved.
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Old 12-08-2018, 02:38 PM   #9
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Re: 2009 Ford F150 engine misfiring


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Originally Posted by DexterII View Post
See this is all part of that "can't remember things any more" thing. And believe me, I'm not being argumentative at all, just finishing the thoughts I had but forgot to mention. Maybe the valve stem seals are indeed worn, and, as I said before, this seems completely plausible given the mileage. Are they worn enough to be a problem, or are they maybe at what one would call normal or even just marginal. Now toss in a loose spark plug, and what exactly does that do? Could it exacerbate the situation? Could it affect the combustion characteristics such as flow and temperature enough to cause excess oil to accumulate? Could a perfectly acceptable amount of oil getting past the valve stem seals become a problem under this condition? Again, not at all being argumentative because I don't know, particularly with only the information that has been provided, but these are the reason that, given what we have, I would run it, see if things have improved with the new plug, run a compression check once things have had a chance to settle, and see how it shakes out from there. Oh, and I would also hook up my OBD reader, or stop by the local auto parts store OP, most of which will run afree scan for you, and see what it shows. And, depending on what they are, I would most likely clear any related codes because the computer could still be trying to compensate for a problem that has already been resolved.
Yes I agree, a tight spark plug might solve the problem.
Then if it doesn't you do the compression test to judge the rings.
Even with a good compression it could be oil rings but it would be worth gambling on the valve seals.
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Old 12-08-2018, 04:15 PM   #10
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Re: 2009 Ford F150 engine misfiring


I did find this

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