CEL, P0307. Pulled the plug and looks like oil is on my sparkplug. What would cause oil to be on sparkplugs?

[PrestonJay12]

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[PrestonJay12]

98 k1500 with 5.7, 83k on ODO. Truck has been running ok, not great. Flashed a CEL, P0307, misfire on cylinder 7. I took it to autozone and used their reading. They said this was the only code showing.

I pulled the plug on #7 and this is what I found. I am not a mechanic, but looks like oil is on the plug. What part or gasket would I have to get to stop oil getting on my plugs? I would prefer to stop the oil fouling the sparkplugs.

I had a misfire on cylinder number 7 or 8 one year ago. Took it to a local mechanic, they replaced the sparkplug and then the code cleared up and so did the misfire. Now it is flashing a CEL.

Two or three years ago, I have a rough idle. Brought it to a local shop, they replaced all the sparkplugs. they said all the plugs were fouled. I didn't ask them why; wish I did ask. The issued cleared up and it ran great. Now the last couple of months, I would take it out and it seems to be running rougher. And If it was a steep hill on the freeway, I would give it gas and it would seem to stumble a bit going over 55mph.

 

[jjester6000]

98 k1500 with 5.7, 83k on ODO. Truck has been running ok, not great. Flashed a CEL, P0307, misfire on cylinder 7. I took it to autozone and used their reading. They said this was the only code showing.

I pulled the plug on #7 and this is what I found. I am not a mechanic, but looks like oil is on the plug. What part or gasket would I have to get to stop oil getting on my plugs? I would prefer to stop the oil fouling the sparkplugs.

I had a misfire on cylinder number 7 or 8 one year ago. Took it to a local mechanic, they replaced the sparkplug and then the code cleared up and so did the misfire. Now it is flashing a CEL.

Two or three years ago, I have a rough idle. Brought it to a local shop, they replaced all the sparkplugs. they said all the plugs were fouled. I didn't ask them why; wish I did ask. The issued cleared up and it ran great. Now the last couple of months, I would take it out and it seems to be running rougher. And If it was a steep hill on the freeway, I would give it gas and it would seem to stumble a bit going over 55mph.

With only 83,000 miles, I wouldn't think that the spark plug fouling would be due to worn piston rings (unless the original owner really didn't take care of it).

I'm leaning towards dried out valve seals. Luckilly, this is a pretty doable job, the only special tool you'd need to get is a valve spring compressor. Does it use oil between changes?

Also, that stumbling at 50 may possibly be the camshaft position sensor, as I had a similar issue with my '98 Suburban with the same engine.

 

[movietvet]

IMO, needs a compression test and document the readings for each cylinder and identify the cylinder and the plug for that cylinder. Do a dry and wet test. Have all plugs out when doing the tests. watch some you tube videos for the procedures. What can cause oil fouling? Rings, guides, seals, pcv problems....etc.

 

[PrestonJay12]

I don't drive it a lot. But from what I can tell between oil changes, oil stays the same. I got it from my Uncle and before that he kept good intervals with changing the oil.

I pulled most of the sparkplugs from the left bank to compare to the number 7 cylinder sparkplug. Out of all of them, #7 was the dirtiest. I found out that number 7 plug was the same one replaced last year and was throwing a code.

I have never changed the valve cover gasket or any gaskets on top of the engine.

Just got done replacing Shocks with new Bilstein 4600.

 

[Komet]

Start with the compression test. Or put a fresh set of plugs in, bottle 'o lucas in the tank, and do some burnouts and full send pulls. See if it snaps out of it. That's not good advice, but it is fun advice.

 

[movietvet]

#7 has a problem and need to see if that cylinder is mechanically sound.

 

[PrestonJay12]

Did some more looking around took pictures. First pic is cylinder 1 and 3. Second is cylinder 7.

 

[Schurkey]

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98 k1500 with 5.7, 83k on ODO.

Flashed a CEL,

Do you mean the light came on, or the light flashed on and off, on and off?

A solidly-lit MIL means trouble. A flashing MIL means SERIOUS trouble, the catalyst is in danger of destruction.

P0307, misfire on cylinder 7...

...I pulled the plug on #7 and this is what I found. I am not a mechanic, but looks like oil is on the plug. What part or gasket would I have to get to stop oil getting on my plugs? I would prefer to stop the oil fouling the sparkplugs.

That plug does not look meaningfully oil fouled to me. I'm surprised it's misfiring. There's oil on the threads, which--based on a later photo of the cylinder head--looks like the oil is coming down from the valve cover gasket.

I had a misfire on cylinder number 7 or 8 one year ago. Took it to a local mechanic, they replaced the sparkplug and then the code cleared up and so did the misfire.

OTOH, that plug does not look as wonderful as I'd hope for given it's relatively young age of only one year. How many miles on that plug?

IMO, needs a compression test and document the readings... ...Do a dry and wet test.

I gave up on "wet" compression testing decades ago. I don't understand how the oil is supposed to go all the way around the rings given that the pistons are flopped-over at a 45 degree angle. Maybe "wet" testing worked on straight-up inline fours and sixes and eights, but once the cylinder bank leaned-over (slant four, slant six, V-6, V8, etc.) it seems pointless. And, of course, adding oil is just adding more incompressible matter into the cylinder, which in itself would raise the compression pressure.

What can cause oil fouling? Rings, guides, seals, pcv problems....etc.

Good call on the PCV. Look for oil in the hose from the PCV valve to the intake system. And make sure the entire PCV system works properly--any pressure build-up in the crankcase could lead to leaking valve cover gaskets, and that seems to be a problem with this engine.

I don't drive it a lot. But from what I can tell between oil changes, oil stays the same.

That can mean one of two things:
1. Good: The engine doesn't consume oil, so the oil level stays constant, or
2. Bad: The engine consumes oil at about the same rate that the oil level increases due to contamination--coolant entry, fuel entry, condensation/blowby moisture, etc.

 

[movietvet]

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Do you mean the light came on, or the light flashed on and off, on and off?

A solidly-lit MIL means trouble. A flashing MIL means SERIOUS trouble, the catalyst is in danger of destruction.


That plug does not look meaningfully oil fouled to me. I'm surprised it's misfiring. There's oil on the threads, which--based on a later photo of the cylinder head--looks like the oil is coming down from the valve cover gasket.


OTOH, that plug does not look as wonderful as I'd hope for given it's relatively young age of only one year. How many miles on that plug?


I gave up on "wet" compression testing decades ago. I don't understand how the oil is supposed to go all the way around the rings given that the pistons are flopped-over at a 45 degree angle. Maybe "wet" testing worked on straight-up inline fours and sixes and eights, but once the cylinder bank leaned-over (slant four, slant six, V-6, V8, etc.) it seems pointless. And, of course, adding oil is just adding more incompressible matter into the cylinder, which in itself would raise the compression pressure.


Good call on the PCV. Look for oil in the hose from the PCV valve to the intake system. And make sure the entire PCV system works properly--any pressure build-up in the crankcase could lead to leaking valve cover gaskets, and that seems to be a problem with this engine.


That can mean one of two things:
1. Good: The engine doesn't consume oil, so the oil level stays constant, or
2. Bad: The engine consumes oil at about the same rate that the oil level increases due to contamination--coolant entry, fuel entry, condensation/blowby moisture, etc.

Wet testing compressions rise as you keep cranking the engine, to a certain point, because the oil in there is being thrown around. It also depends how much oil you put in the cylinder. I want to see if there is any difference, even if it is minimal and I still compare. We each know what works for each of us and gives us the info we are looking for.