Oil on Spark Plugs

JBlaw22 · Jan 25, 2009

I was changing out my plugs today and found two of them covered in oil (the thread/electrode end)…the oil was wet (not burned on the plug). My first thought is piston ring going bad letting oil into the cylinder…..what are your thoughts? Any other causes of this?

If that’s the case…how difficult is it to do a ring job on these motors…I assume that I have to pull the motor, correct?

If it turns out I have to pull the motor and tear down the top end of the motor…what other things should I replace/upgrade to "renew" the life in the motor?

2002 Mustang GT 4.6L V8 with 87k miles

Thanks in advance for any help/insights!

AdRock · Jan 26, 2009

I think I already answered this somewhere else. But I'll do it here too. It's most likely your valve covers leaking into the plug holes. The oil pools uo them coats the threads and electrode when you pull them out,

Check that FIRST, it's cheaper than tearing down the engine.

superstang46 · Jan 26, 2009

AdRock said:
I think I already answered this somewhere else. But I'll do it here too. It's most likely your valve covers leaking into the plug holes. The oil pools uo them coats the threads and electrode when you pull them out,

Check that FIRST, it's cheaper than tearing down the engine.

+1 I've seen this before also. Definitely the best place to start.

JBlaw22 · Jan 26, 2009

AdRock said:
I think I already answered this somewhere else. But I'll do it here too. It's most likely your valve covers leaking into the plug holes. The oil pools uo them coats the threads and electrode when you pull them out,

Check that FIRST, it's cheaper than tearing down the engine.

LOL Thanks for the reply...again!

the plug wells had a little bit of dirt/grime/oil on walls, but it looked like it had been there a while. I could see the "shinyness" of the aluminum at the bottom of the wells, so I don't think it was leaking in from the top.....

Here's a picture of the plugs:

mrvax · Jan 26, 2009

Jason, those plugs aren't oil fowled. Are the 2 that had some oil on the same side of the engine where you add oil? With my first Mustang, I accidently dripped some oil when adding and got some down in the plug wells.

crazystang25 · Jan 26, 2009

yea it could be those and if it isnt the valve cover gasket the next place i would look is valve seals. just a thought (still cheaper than tearin down the rest of the motor)

SADL-UP · Jan 26, 2009

How is the motor running? If is is running rough, then its possible that you have a mis fire (from a bad COP). If the spark plug is not firing then you should expect to see a buildup of gas/oil on the tip. If the car seems to be running fine then I would do a compression test on all of the cylinders and compare the numbers to the two cylinder where you found the oil. This will give you some insight as to whether the problem is mechaincal (rings, valve seals, etc.) or electrical (bad COP, leaking injector, etc.)

HTH...

JBlaw22 · Jan 26, 2009

mrvax said:
Jason, those plugs aren't oil fowled. Are the 2 that had some oil on the same side of the engine where you add oil? With my first Mustang, I accidently dripped some oil when adding and got some down in the plug wells.

The two "oily" plugs are from the drivers side (opposite of the oil fill)

crazystang25 said:
yea it could be those and if it isnt the valve cover gasket the next place i would look
is valve seals. just a thought (still cheaper than tearin down the rest of the motor)

How do I determine if the valve cover gasket is leaking? Is it just a replace it and see what happens kind of thing?

SADL-UP said:
How is the motor running? If is is running rough, then its possible that you have a mis fire (from a bad COP). If the spark plug is not firing then you should expect to see a buildup of gas/oil on the tip. If the car seems to be running fine then I would do a compression test on all of the cylinders and compare the numbers to the two cylinder where you found the oil. This will give you some insight as to whether the problem is mechaincal (rings, valve seals, etc.) or electrical (bad COP, leaking injector, etc.)

The motor was running fine, with the exception of occasionally it would bog down and run very sluggish - almost as if it was going to stall and had no power at all. This would happen while I was driving at highway speed and would last for about 10 seconds then go away. The ECM threw a code and it gave me a MAF error.

Now for the new news......................................................................

I ran the compression test (heated up the engine to operating temp, removed all spark plugs, unplugged wires from coil packs, went through each cylinder with the compression gauge)

All the cylinders were right around 200psi +/- 2psi, except one which was at 182psi. Note that this was NOT one of the cylinders that had oil in it (it is adjacent to those one though).

So the next step, I poured 1 capfull of oil into each cylinder via the spark plug opening through a long skinny funnel to prevent as much leakage as possible.

I connected the compression gauge to one of the "problem" cylinders and turned over the motor 4 times. the compression gauge maxed out on that cylindar and the adjacent one (the other "problem" cylinder) spewed oil all over the engine bay and was smoking like a chimney. Non of the other cylinders were smoking......

JBlaw22 · Jan 26, 2009

Ok, I feel like a schmuck.....I realized that I didn't block the Throttle Body open to full throttle when I did the compression test, my guess would be that is what explains the ridiculously high psi and the launching of oil out through the open spark plug well.

Once I realized that, I figured that I would try it again, correctly this time. So, I put all the plugs back in and wired everything back up to to let the car run and warm up again. Well, now the car won't even turn over....

How much did I just screw myself?

crazystang25 · Jan 26, 2009

ya if u said it was spittin oil out of the plug hole then you gotta prob. cause there shouldn't be any in the cylinder at all. so next you need to find where its gettin through.

JBlaw22 · Jan 26, 2009

Ok, I got the car started, I went through all the plugs and electrical connections and disconnected/reconnected them, removed all the plugs, re-seated them. Then just for grins, I charged the battery. She coughed and gurgled, but eventually turned over.

So now I am seeing white smoke from all ends....the exhaust (driver side tail pipe) and from the engine bay, it's coming up from in between the firewall and the block.

Now I'm wondering how much of this is due to the spilt oil from our little oil explosion earlier today and how much of it is actually internal. Do you that the white smoke coming from the tail pipe is due to the oil I added to each cylinder during the compression test????

I let it run for about 30 seconds and the smoke quit coming from the engine bay, however, when I opened the throttle just a little bit, it started in the engine bay again. I didn't want to let it run to long and cause further damage so I didn't get to pinpoint the exact location on the motor where it was coming from.....

Now the question of the hour to those blessed with more car knowledge than me.....Where does this leave me? Should I try to do the compression test again? Is the white smoke indicative enough to make the decision to pull the motor and look at the cylinders/pistons/rings?

crazystang25 · Jan 27, 2009

i think based on what your telling me that the oil from the fire wall might be from some of the oil that was spit outta the cylinders, and it was running down the back of the block. but the smoke from the tail pipes is from the motor burning the oil. now of course you have to figure out where its gettin in the cylinders from. i would let it run for a minute or so though so you can see if it continues to burn anymore oil then go from there, cause if its from a ring or valve seal it wouldn't hurt it anymore. you would have to rebuilding one of those parts if it is anyway.

AdRock · Jan 29, 2009

All that smoke you are seeing is the oil that you put in the cylinders burning off. If you let it run for a while or just go drive around it will eventually quit smoking.

At this point, my advice would be to clean all the plug holes very well. Also clean off the plug boots and the intake surface around the plug holes. Put everything back together and just drive the car like normal. If it's not missing and runs fine(except for the MAF problem you mentioned) then just keep driving it. After about 30 days pull the cops off and see if there is oil in any of the plug holes. If there's not, then pull the plugs again and see if any are covered in oil.

I'm betting that this is something very simple that is just being overanalyzed.

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