996 cylinder missing only when engine cold

[Josh Kirkpatrick]

I have a 2002 996 cabriolet. The CEL came on (I don't have the code), then it started blinking, and the engine was missing noticeably. I was headed to the airport, so I took it to the dealer and caught a cab. The dealer has had it for a month and says that one cylinder is missing when it's cold, but once the motor warms up, it runs fine. The dealer has tried replacing the plug wires and ignition coils but has been unable to diagnose the problem, even after speaking with the Porsche North America folks. Now the dealer is saying they need to pull the engine and take it apart ($3500 bucks), thinking that there is a bad lifter on the cylinder or perhaps a crack in the cylinder. Has anyone encountered this problem? Any ideas that the Porsche folks haven't thought of that could save me some big bucks? Thanks.

[Loren]

Did they swap spark plugs from the missing cylinder to a known good cylinder?

[Josh Kirkpatrick]

The dealer says they swapped the plugs, plug wires, and coils, and it continued to miss on the one cylinder. I'm not sure if they tried the bad cylinder's plug in a cylinder that wasn't missing, but I can suggest that.

[Dharn55]

It is a simple test to see if there is a spark at the cylinder/plug. If there is spark then it could be a stuck lifter, bad injector, sticking valve. I would certainly check the injector first. Run a compression and leak down test, that should show a cracked cylinder (doubt that is the problem). $3,500 is too much to drop the engine and pull off the valve cover and cams to replace a lifter.

Where are you located?

[Josh Kirkpatrick]

Denver, Colorado