Cayenne COILS + PLUGS
One of the known weak points of the cayenne is the coils. They have a habit of failing prematurely on quite a regular basis. The symptom is a misfire or lumpy, impotent engine especially around the low to mid 2000's. This is often experienced on the motorway when in 6th gear but also noticeable when idling as the revs will drop quite low.
I had these symptoms once after a very long and hard motorway journey and my engine check light came on but the next day the light had gone out and the problem went away.
A month later though and it came back and it felt worse and wouldn't go away so I had to investigate.
Its worth first of all working out if the plugs are at fault or the coils. Also, common sense says that you should change ALL coils and ALL spark plugs at the same time. That's not what I did but that's what you should do in theory.
Remove the front and side plastic engine bay covers with a wide flat bladed screwdriver. As you unscrew the quarter turn fasteners, pull them out or else you risk losing them down into the engine bay.
At the back of the engine bay you have the 2 air pumps. Take these off their rubber couplings with a T40 torx driver. There are 3 screws on each.
You can simply wedge them up and out of the way once they are dismounted.
On the LHS you have an engine brace. You need a 12mm triple square socket for this and a 16mm the other end.
The other end is another 16mm screw head that goes into a captive nut. Undo this or just loosen so you can swing the arm up and out of the way.
Now you just need to remove the mounting bracket for the torque arm. Use a Torx E12 female socket here.
Now you can remove the plastic 'porsche' covers. You have 4 torx T30 screws on each one,
Some of these dont have much space around them so a slimline ratchet and socket is useful or a little bit ratchet liek I use.
Slide the covers out.
The LHS one (as you are looking at the car) is a little tighter against the pump bracket.
Now you have to unclasp each coil with your Torx E12.
The connecters can be pryed off with a basic flat screwdriver. Just twist it in the gap as you press the hook down on the connecter with a finger.
What you can do is run the engine then pull each coil one by one. If you hear it sparking against the metal block when you pull it out fair way and it makes the engien sound even more ill and lumpy then its working. If there is no effect then either the spark plug or coil is shot. The best thing is to swap them around to see which one is at fault.
Here's a new Beru installed. You are advised to change the lot as they have a habit of all failing at the same time. Reassembly is just the reverse of the above.