I've been having a starting issue with my 1999 996 (about 95,000 miles, automatic) since mid-November. Sometimes the car will start up just fine. Other times, with no rhyme or reason as to timing (sometimes cold start in the morning, sometimes warm start after car has been parked for 30 minutes to a few hours, etc.) the car does not want to start up. When I turn the key I will hear the "na na na na na" sound which could last up to 10 seconds or so. Then sometimes the engine will fire up and die right away. Eventually, after repeated starting attempts, the engine will start up. Otherwise, the car drives just fine.

Yesterday, had a new symptom pop up. Was trying to start the car and then heard a "boom" behind me and white smoke coming from the engine compartment. No fire. Let the car sit for 5 minutes and eventually got it started.

Car has been taken to multiple mechanics who either (1) can't replicate the starting issue after numerous attempts; or (2) have the issue but can't figure out what it is. First time around, Porsche mechanic (independent shop) was able to recreate the issue once and told me that fuel pump needed replacement. After replacing the fuel pump, problem still happened. Next time around at a different Porsche shop (dealership), mechanic could not replicate the starting issue, did a full inspection of the car, and told me that the ignition coils needed replacing because of hairline cracks so we replaced all the coils as well as the spark plug. Problem continues.

Any thoughts would be appreciated. I've dumped close to $2000 on repairs between the fuel pump and ignition coils and don't want to do any more repairs until someone can tell me the problem.

Thanks much!

 

I had a starting issue on my 2000 996 several months ago. Also changed the fuel pump but the issue was still present. Symptoms were a bit different from yours. What initially appeared to be an intermittent starting problem turned out to be a repeatable starting problem after every gas fill up. Turned out to be some pressure valve in the gas line. I would need to pump the gas pedal like crazy to get it started. Replaced the valve and no problems since then.