Oil on spark plugs

[cayennea7]

Hi guys, I recently replaced all my spark plugs and noticed trace of oil around the threads of spark plugs on cylinder bank #5 and # 8. I'm thinking the spark plugs gaskets need to be replaced. How hard is it to remove the valve cover. Any tips to tackle this job? I looked but did not find any DIY on this site. Any help would be appreciated.

[clarksongli]

Pretty easy job....put it on the difficulty level of redoing the cooling pipes.

If you look into the hole do you see oil....maybe the plugs are just fouling because of a bad coilpack?

[cayennea7]

I didn't see any oil when I looked in the holes. Could you elaborate more on the bad coilpack? I have a 2008 cayenne s if that helps. Thanks again for your reply.

[clarksongli]

well if the plug is fowling (not oil dripping down onto the plug), then it means the plug isn't firing, or firing very weakly. Because we use individual coilpacks on each cylinder, it usually points to a bad coil on the sparkplug.

An easy way to check this is swap that coilpack to another cylinder and drive it around....check the spark plugs again.....if the new cylinder is now "oil covered" or fowled, then it's the coil pack....but if the fowling stays with in the original cylinder and doesn't follow the coilpack, you know it's something cylinder/gasket related.

how did the electrode look on each plug? clean and lighter ash colored? or dark and oily?

[cayennea7]

Hey clarksongli, thanks for your input you have been a big help. The spark plugs looked normal to me light dark brown color. I will switch the coil pack around to see if there any changes.

[9552T500]

I am trying to figure a related issue with oily plugs and misfiring on my 06 Ctts. All started with occasional shaking w/o noticing any response issues or other alerts (wife's description who drives the car most). Myself got solid MIL upon starting the engine and after a few miles shaking and significant response loss. Felt like sth. out of balance. OBD-II showed P0307 and P0357 & started digging into spark issues on bank 2. Since this is my first time I do this with this car and I did explore things myself - here some docu- which may help sb. else going through similar issues first time: CayenneTurboS_troubleshooting_p0307_p0357_sparkplug_coil . My coils are rev 03 coils, but having no visual damage, so that I tried to circle the issue by swapping the oily plug #7 with # 6 (which color looked OK - see fig 17 linked). I tortured the car for 20 min, but failed reproducing cylinder failure. However the MIL remained on. I re-checked the plug color (Fig. 26), and both plugs started to look more alike with carbon starting to burn off/easy peal off residue on original #7. I reversed plug swap and got misfire right away. This has been double-checked, and turns out to be repeatable. I also tried to swap the coils, but this did not change anything to the better.

My conclusion by now is that I may have too weak coil(s) to cope with pretty old plugs with plenty of residues /starting electrode burn-off. According to my records these plugs are almost 40k in the car, so they would be due for the 80k anyway. I will get them this week and hope that's it for this time. What puzzles me though is that a simple plug swap seem to fix the issue - at least temporary. I am also wondering how long I need to wait until MIL disappears or whether I have to reset manually. Any advice is appreciated. THX

[clarksongli]

the MIL will reset after a few driving cycles, but will log in the NVM for future reference if you pull the code history.

But like you said, if you do a quick reset, then you know where you are without having to wait.

I'll be honest, very few times have i ever seen plugs as the actual problem.....they are a very simple design, and as long as they are the stock temperature range for the motor, then there is no reason why a plug would all of a sudden stop working. I have had one incident where i burned an electrode off while on the dyno stand doing some tuning, but otherwise, never.

Plugs usually represent an issue with something else (fuel/air/electrical). If you move the coil again, i would drive on it for a while

[9552T500]

.....as long as they are the stock temperature range for the motor, then there is no reason why a plug would all of a sudden stop working.

Plugs usually represent an issue with something else (fuel/air/electrical). If you move the coil again, i would drive on it for a while

Thx - I've got he next code P0300 now, and misfiring again..... So, will check once more with swapped coils, but I possibly I will simply need to exclude the plugs ASAP and eventually coils in parallel. When you mention temperature range - do you think engine overheating ~ 1.5 k miles ago can have had impact on a plug failure now (coolant expansion chamber was cracked...)?

[9552T500]

OK- new plugs coils and install is completed on the left bank (now 09 coils). Still will need to finish the rhs bank, but so far it fires up sounds and turn smoother per first impression....

[clarksongli]

no when i talk about temp range, i'm referring to the combustion temperature, not coolant.

basically plugs are designed for combustion performance....for naturally aspirated economy driving, you typically see a higher temperature range because the burn and flame front is not a large concern (they will typically run large overlap on the intake and exhaust valves to improve fuel economy as well)

for a high performance forced induction motor, there is much narrower tolerances for burn rate and flame front in the combustion chamber. Because you are approaching the limits of the octane being used, pre-detonation is more of a concern than with an economy based motor. To reduce this risk, you will see everything from pulling timing, reducing AFR, or a lower temperature plug. The idea is that if the plug runs cooler, there is less activation energy present to cause the detonation....allowing for increased power levels without risk.

[9552T500]

no when i talk about temp range, i'm referring to the combustion temperature, not coolant.

... The idea is that if the plug runs cooler, there is less activation energy present to cause the detonation....allowing for increased power levels without risk.

Well - I meant overheating of the chamber with stock plug temp range as consequence of reduced heat transfer through the smaller temperature gradient due to faulty cooling system....