Engine sputtering under load - need diagnosis
 

After having the car on stands for 4 weeks during a complete suspension rebuild, I took the car out to the track for its break in run.

Unfortunately it did not go so well. The suspension felt great but under full throttle the engine would sputter. It felt like either a fuel delivery problem or an engine misfire. In particular the problem occurred on hard right hand turns as I went to full throttle approaching and passing the apex. It also happened on a fast left hander as well. I don't recall the problem happening during straight line acceleration but it consistently happened on these three turns. Fuel filter and fuel pump each have less than 1000 miles on them. I also noticed that the car did not idle like it used to. The rpms were a bit low and it sounded different, like it was stuggling a bit.

Any ideas on what to look for?

I would wager my $$$ you've got a fuel related problem; 4 weeks sitting up might have created some fuel sediment issues. I've not personally encountered this problem, so any suggestions I would make will be just an educated "guess". Perhaps drain/clean the gas tank, put some compressed air to the lines you can easily access and clean up or replace the fuel filter....maybe a shot of Techron as well. Keep us posted on the final fix.

I thought bad fuel was a possibility as well. On the first run I had a little less than 1/2 tank. I then went out and filled up to get some fresh fuel into the tank before the next run. No change. A bottle of Techron certainly wouldn't hurt, though I now need to empty the tank before putting it in.

The fact that it only happens when the car is loaded in a turn makes me wonder if there is a fuel pick-up issue.

Any other ideas out there?

Maybe you pinched the fuel line with the jack stand? I am not sure its possible on a 911, but something you could check.

less than a thousand miles on fuel filter would rule it out i would think. what about the weather? it's been hot as balls lately..could you have a bad o2 sensor..or maybe need to adjust mixture (running lean at wot) to compensate for thinner air? did you own the car last year? see anything similar during the scorching season last year?
ryan

do the kiss method...could also be a secondary break dwn. either scope it or slam in a new set of plugs (cheaper then going to the shop)