I have a 2004 40th anniversary which comes with the X51 engine. The engine tends to buck when starting out at light throttle. Not an issue with more throttle. It seems to be running lean, on the threshold of stalling. Anyone heard of this?

 

I have an X51 in my 996. I don't have this issue (knock on wood). However, when I did the PPI on the car, I believe 2 spark plugs were loose. You might want to start there?

 

Mine does that once in a while too. I was considering starting a thread on this as well. I thank the bucking may be a result of not giving it enough gas as you release the clutch. Or could it be a sign of bad RMS? I replaced my RMS and clutch about 9k miles ago.

 

Mine was doing this a few days ago. Even threw a check engine light. Dealer said it could be because of winter gas or I started the car with my foot on the gas. Well who knows. I got a check engine light the other day again so I add some fuel system cleaner with about 1/4 tank of gas left and then disconneted the pos battery terminal. Light went away and engine remapped the fuel settings. Running 1000% better now.

 

I was having similar problems (non X-51) and I needed new spark plugs and found that 2 coil packs were cracked. Per Porsche the plugs should be changed every 60K miles, OR 4 years... I had the original plugs, my car is a 2002. Much improved now.