Hello, I have the following problem with my 2005 Cayenne TTs. When opening throttle, I have full boost for some seconds, engine is slightly hesitating and rattling in this condition (0.8-0.9bar boost). The boost is the reduced by ECU to 0,4 bar after some seconds, engine is running fine with this low boost. Plugs are new, engine has nearly 100000 miles now. There are no fault codes listed in ecu. Coil problem?

 

coil/s.......floor it and see if the check engine lights starts blinking...

 

I just removed all spark plugs again, one plug is bad and seem to have a damaged electrode, although they had been renewed 12000 miles ago. I also checked the coils, they are already the "newer" version 948.602.104.05 from Beru. I will renew all spark plugs again and check if thats the problem.

 

Any chance you could show a picture of the damaged plug? Would like to see what might have caused it.

 

Maybe the coating of the electrode was not ok, it`s a bosch super plus spark plug (FR6KPP33+)

 

Those plugs look terrible for only 12k miles.

 

Try swapping coils.

 

You said its "rattling" you sure thats not knock? Maybe the ecu is cutting boost cause senses theres a problem. Also a boost leak will make you lose boost and will also cause knock.

 

This rattling definately sounds like knock to me. These plugs look like they are not running in the correct heat range also, that one plug looks like it is oil fouled as well as having the electrode partly missing. Hard to believe that is 12000 miles. I would run the NGK Iridiums, make sure to be very careful when gapping them. I would also look into the possibility of oil fouling (excessive oil from pcv in system) and check for leaks at all the connections. What brand gas and octane are you using? Also a good point about the coils, maybe you have an issue with them again.

 

Hey snzuloz - how can you tell about oil fouling, i.e., checking for leaks? I had a similar coil issue after changing coolant pipes on my '04 CTT a few months ago. Pulled the plug and it was oily. Cleaned it off, swapped coils, and all seemed fine. I haven't checked again.

 

I'm assuming that when you swapped coils you replaced them? The only way to check for oil fouling is to inspect the intake ducting (especially drivers side) as they seem to pull a lot of oil in from the pcv on this side (turbo compressor outlet area), which eventually deteriorates the o-rings and causes external leaks. Obviously the oil will eventually migrate with boost and get into everything along the intake tract. If your plug wasn't firing properly it would be easy for any oil to build up and foul the plug over time. I think the only option is to reroute the pcv so it either hits a catch can idea or replumb it higher in the system so oil isn't drawn in so easily.

 

Problem is solved after installing new NGK platinum plugs (PFR7Q). Engine is running smooth again and full boost is available.