Iffy ignition coils on my 2004 CS

[Rod Croskery]

The problem is not that the aftermarket coils on my Cayenne S occasionally fail, it's that they don't fail enough to trip the check engine light so that I can identify which one is the culprit.

 

A couple of months ago #2 blessedly quit in city traffic only an hour from home, so I isolated the culprit (under the engine mount) and had it changed shortly after we arrived home. It had fixed itself once on the highway and run normally on the retreat to my shop. The spark plug had worked its way loose, even though I had torqued them all to specifications at the time of installation along with the new coils two months earlier.  Up until the point of the code 302 popping, I had gotten into the habit of downshifting in anticipation of a miss whenever I had to slow down in traffic. 

 

But there's still another coil missing a little bit, occasionally.  

 

Short of replacing them all with OEM products, does anyone have a way of testing the coils before they get so bad that a code pops up?

 

Has anyone else noticed a loose spark plug after a bout of missing?

[JFP in PA]

Unless the plugs are properly torqued, with a dab of anti seize on the threads, they will come loose.

 

Your message contains the magic word: "Aftermarket".  We have had very inconsistent luck with aftermarket coils, and have stopped using them.

[Rod Croskery]

After a series of coil failures on my '04 CS I bought a set of eight OEM coils from the local dealer.  The car immediately became much more drivable, though the fuel consumption was unchanged.

 

Amazon.ca is an amazing shopper's resource, but not for Porsche ignition coils.

 

Now I'm getting P0155, indicating a problem with the heater on the pre-cat oxygen sensor on the left side.  Has anyone found a source of reliable O2 sensors at a good price?  Will one do, or will all four need replacement?

Edited December 4, 2018 by Rod Croskery
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