FiatCoupe

I changed the spark plugs on my 2007 C4S yesterday at 60,000 miles. Many thanks to this forum for an excellent guide and community. I removed the silencers which made the job easier. Whoever designed the exhaust mounting brackets needs a slap.

4 of the plugs have relatively easy access. However the two behind the bracket require some effort. I had to use a spark plug socket, then a 6" extension bar, a universal joint, a 4" extension bar then a converter from 1/2" to 3/8" to enable my 3/8" torque wrench to fit on the end. It worried me for a while about feeding in the spark plug socket into the hole then following it with the extension bar.

I used my new Jackpoint jack stands to rise the car, very pleased with them

Anyway all the plugs bar one look perfect. Yes they are worn and I'm glad they are being replaced. The colour and condition look great. However one of them, the one nearest the front of the car on the passenger side (#6 I believe) looks differrent. It's not damaged in any way but the colour is darker and it has a wet finish. The top of the piston also looked wet. I've looked at plug condition guides but it doesn't match any of them.

I'm not sure what the cause is. Maybe the coil isn't firing and it's fuel on the plug? I would expect it to be blacker if it was oil fouling? It wouldn't be the first time a coil has failed and not triggered a CEL.

The plug on the left is a used one which looks in good condition, the one on the right is the one I'm concerned about:


Does anyone have any ideas?

Would this be covered under warranty. It's CPO until April! Before I fire off an email to my service adviser I'd like a better idea as to what the problem might be.

Many Thanks

John

fpb111

Looks like oil fouling. What did it smell like? Gas? Oil?
Maybe run a leakdown test?

http://www.verrill.com/moto/sellingg...colorchart.htm

San Rensho

Looks like oil fouling to me. Definitely tell the dealer about it to create a paper trail. Next thing to do is a compression check, leakdown test and possibly a boroscope to determine where the oil is comiing from. Could be as benign as a bad valve guide seal, or worn valve guides or worn rings or bad cylinder.

neanicu

How's the car running? Is she smoking?
I'd say it's just unburned gas and some carbon buildup.
Why only that 1 cylinder? Good question. Depends which cylinder it came out of...I think it might have something to do with the firing order...
I wouldn't worry about it unless the car is running poorly or smoking.
You have no idea how many Internet diagnostics I've read around that turned out to be NOTHING...

FiatCoupe

I sent an email to my service adviser together with the picture. They say at the moment there is nothing warrantable based on what I have presented. They do agree that the plug has a lot of residue on it compared to the others and will inspect the car for me.

I'm putting the car back together and fitting new coils. That should eliminate the problem being plug or coil. I'm off to COTA this weekend so that should put a couple of hundred miles on the car. I'll pull the plug when I get home (after engine is cold) and check it again. If it's still wet, which is what I expect, I'll take it to the dealer next week for them to inspect.

The CPO expires in April so this is a close one! Finding a problem wasn't what I wanted to see when I changed the plugs but at the same time I'm glad I did and know there is a problem now.

John

neanicu

Meant also to mention/ask :
Do you do a lot of stop and go traffic,short trips and sometimes don't bring the car to temperature(and by temperature I mean oil temperature not coolant)?
That's how a spark plug will look after those kind of trips.
If they weren't so damn hard to get to,I would pull one out after some highway miles at speed. They should all look like the first one you're holding...

CORSASCHNELL

The condition of all plugs should be about the same for a normal engine at a given mileage. The fact that one plug looks much worse than others indicates a problem with that cylinder. As said above, a compression check might reveal much valuable info for you.

neanicu

I agree with this statement : ABOUT the same.
I don't know about much worse...
My first suspicion would be a misfire on that cylinder,even if it's not a severe one to be picked up by the DME : like a poorly performing coil.
Why think of the worst at 60K?!
Anyway,have it checked out...

mdr2001

John,

I changed my plugs today - 2008 C2S with 29,550 miles. Here are the plugs I pulled from the passenger side (pic1).

Pic2 is a closeup of a new vs the "worst" plug I had.

Pic3 are the passenger coil packs - all were in great shape and looked new after some cleaning.

Pic4 are all the Spark plugs and correspond to car extraction point - left=driver side and Top = front of car.

Hope this helps.

neanicu

Thank you for posting this!
Please look at the difference between plugs.
Does that mean you have oil making its way into the combustion chamber due to worn out piston rings on the respective cylinders? NO!

mdr2001

interesting question. To be honest, after seeing others' posts regarding Spark plugs - I assumed this was normal. See this post for a picture and a few comments that say theirs looked oily.

https://rennlist.com/forums/997-foru...plug-wear.html

I did notice the passanger side and Front driver - 3 plugs total- had more oil while the remaining 3 were quite dry. I would like to hear from the experts, but since there was no fouling, I assumed it is not an issue.

anyone??

neanicu

I've answered my own question previously :
No,it is not an issue!
I'd be very interested to hear different opinions as to why this is an issue...

mattyf

Look up 997 cylinder scoring. I'd show the dealer the plug and see if they could boroscope the cylinder for you.

FiatCoupe

I put 425 miles on the new plugs driving to Austin to watch the GrandAM racing at COTA. Very impressive cars and drivers. Here is a little video clip from one of the bridges:


The next day I removed the plug from cylinder #6 and it still looked like new. I performed a cold compression test on #6 and it read 275 psi which was exactly the same as on cylinder #5. A hot compression test would be useful.

I have a cheap eBay boroscope which is okay, I cold see the valves and piston but it's not very good at looking at the cylinder walls.

I think I'll still take it to the dealer this week for them to use a good boroscope on the cylinder. It should be pretty easy and quick for them to do on #6.

John

Mark Harris

The sound of those cars passing under you is awesome. What kind of camera did you use for that? Thanks for sharing.