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Discussion Starter · #1 ·
I have 2001 Mustang GT that is getting oil on the spark plugs, and I am trying to determine if it is worth changing out the valve cover gaskets or if the problem is something much worse. The oil is on the threads as well as on the boot and on top of the plug. What might be causing the oil on the threads?
 

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Discussion Starter · #3 ·
The electrodes look normal(tannish) unless the engine starts misfiring on that cylinder. Once the spark plug fouls then the electrode goes white. If I pull the plug out that is missing, clean it and put it back in then it goes back to the normal(tan) until the oil gets on the plug again causing it to foul again. It doesn't appear to be an isolated issue either. It has happened on 5 different cylinders over the past 9 months. It also starts throwing codes P1151 and P0155 once one of the cylinders misfires. Are you referring to changing out the valve cover gaskets?
 

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When you say "oil on the plug", are you referring to oil on the business end of the plug, the tip and side electrode in the cylinder; or the top of the plug--in the plug well?
 

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Discussion Starter · #5 ·
On both ends of the plug. Its not from oil being spilled on it, because it happens on the opposite side of the oil filler as well. To be honest I am not sure that I have noticed whether or not its on the tip or just on the threads. If it is just on the threads, that could be from when I am removing the plug and the oil sitting around the top of the plug. I can't say for sure though. The oil is also on the coil pack insulator boot.

Just in case it makes any difference at all: Today it throw a misfire code on cylinder 2, and was running horribly. When pulling the plug out of two, cleaning it off, and re-installing, the car stars to run great.
 

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If it were fouling from bad rings or valve seals the tip on the plug would be sooty and black looking--what you describe sounds like oil in the plug well. A bad cam cover gasket can do this; however it should be rather obvious that it is leaking as it takes quite a bit of oil to foul the plug well...
 

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When you say "oil on the plug", are you referring to oil on the business end of the plug, the tip and side electrode in the cylinder; or the top of the plug--in the plug well?
I agree. It is very confusing. How can valve cover oil cause fowling of a spark plug? (We are talking about fowling at the prongs.) Actuallly, that is not very likely. Well, that was being nice. It is pretty much impossible.

If you are getting oil on everything then you shoud change the gaskets.
 

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Discussion Starter · #8 ·
I am sure that the valve cover gaskets are leaking, but just wasn't sure if I wanted to replace the gasket or if it would just be a waste of time. I have tested the compression on the cylinders and they are all pretty balanced, and now the car doesn't seem to be losing any power. If it were bad valve seals or rings wouldn't it result in some loss of power? Also I do seem to remember there being some sort of black particles on the "business" end of the plug.

In the event that it is bad rings or valve seals, does anyone know of a good step-by-step to performing the replacement of either of these? Or even any good advice before taking that on?
 

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What are you looking for? Yes, bad seals and bad rings would show up. You know this as well as I do. What is it you want? Do you want justification for your wife to spend money on a new block? You just said that your compression ratio is good across all cylinders. From what you have posted your motor is in better condition than mine, but mine still puts out 380 rwhp.

What is it you want>
 

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Discussion Starter · #10 ·
I agree. It is very confusing. How can valve cover oil cause fowling of a spark plug? (We are talking about fowling at the prongs.) Actuallly, that is not very likely. Well, that was being nice. It is pretty much impossible.

If you are getting oil on everything then you shoud change the gaskets.
I guess technically we are not talking about fowling at the prongs, because after just wiping the plug off (not using cleaner just a shop towel) it is no longer missing on that cylinder.

If there is oil on the top of the plug and on the boot would it not affect the spark plug continuity?
 

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That is a different problem, requiring different solutions. Yes, if the COP is shorting out then that would cause a misfire.

If you are drowning your COPs in oil then you need to change the gasket. I've thought about it. I don't know of any other way that oil could get that high on the motor.
 

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Discussion Starter · #12 ·
What are you looking for? Yes, bad seals and bad rings would show up. You know this as well as I do. What is it you want? Do you want justification for your wife to spend money on a new block? You just said that your compression ratio is good across all cylinders. From what you have posted your motor is in better condition than mine, but mine still puts out 380 rwhp.

What is it you want>
I have put countless hours of work into this car, and I am just a bit burnt out and hoping not to have to continue to pour more and more hours to no avail.

Just to give a brief history:

May 2012 I swapped the motor that was hydrolocked, but after install the motor wont start. No fuel pressure, but it is cranking. Went through everything that I could think of to fix the issue to no avail.
June 2012 Took the car to the dealership to tell me whats wrong and fix it. They said it was the computer so I purchased a new computer, and had them flash it..still wont start. I leave it with them to get it running 7 weeks later they call, and said that it was running but didn't know how they did it.(Go figure) They also say that they found a wiring harness that had melted several of the wires together causing a ton of issues. They said it would cost at least 2500 to overlay the harness, because they couldn't find one. I decided to take the car home, and do it myself. The wiring harness that runs from the drivers side fender through the firewall and interior to the trunk.
July 2012 Wiring harness overlayed, and btw the car was missing on 5 cylinders when they gave it back to me. Bought and installed all new coil packs, spark plugs, 02 sensors, etc. Temperature and a/c wasn't working either. Fixed those by replacing the ECT. Passenger side headlight not working either due to wiring issue, so I pulled that one too, and overlayed it as well. Light works now.

The list goes on, and on, just trying to see if anyone on here my be able to shed some light on an area that I may not be thinking about or don't know for that matter.
 

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No offense taken but I still can't see a condition where oil out of the valve covers fowls the plugs. Now a misfire is different. You could drown the COP in oil. But that would have to be a lot of oil. It would be noticeable, don't you think?
 

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Discussion Starter · #16 ·
I will be changing the valve cover gaskets and pulling the plugs again to test compression. It has been a couple of months since my last compression test round. I will try to post some pictures of the plugs and COPs, and the second compression test results to give a more precise description of what is going on.
 

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" The oil is on the threads as well as on the boot and on top of the plug".

Sounds to me like you may have spilled some oil while changing or refilling around the filler neck. There is no way the oil can leak past the plug threads and enter the cylinder unless the spark plug is so loose its ready to fall out and at the same time you have a massive Valve cover leak.

If you have oil in your spark plug well excpect the car to run terrible if the oil is deep enough to cause misfire.

You said there is oil in the cylinder side of the plug that that can only mean one thing your rings are not gapped properly or they are on thier way out. The only way oil can get past a ring is if its simply not sealing and wiping. you should notice some significant black smoking if this is the case.

Did someone build the motor you have in there now? If so they could have gotten one of the ring gaps wrong because each ring has a specific gap in order to seal properly.
 

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I will be changing the valve cover gaskets and pulling the plugs again to test compression. It has been a couple of months since my last compression test round. I will try to post some pictures of the plugs and COPs, and the second compression test results to give a more precise description of what is going on.
A compression test could only give you insight as to what would be causing oil on the electrode of the plug not oil filling the plug wells. From your description, it sounds like the oil filling the plug wells is what is causing your miss. Looking back at pictures, I just can't see how oil would defy gravity and leak back into a plug hole as opposed to leaking down towards the exhaust manifolds. I'm not saying it doesn't happen, I'm just concerned that it is!
 

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A compression test could only give you insight as to what would be causing oil on the electrode of the plug not oil filling the plug wells. From your description, it sounds like the oil filling the plug wells is what is causing your miss. Looking back at pictures, I just can't see how oil would defy gravity and leak back into a plug hole as opposed to leaking down towards the exhaust manifolds. I'm not saying it doesn't happen, I'm just concerned that it is!
I agree, it would have to be some sort of insane oil leak from the cam cover to flow in that direction and flood a plug well...

OP, looking forward to those photos!
 

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I had oil on my spark plugs from my pcv valve being clogged and not releasing the pressure from the crankcase and pushing the oil past the valves. It was piled around the threads on the spark plug and causing the plugs to ground out and misfire really badly.
 
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