Ernie J

Have miss @ 6000 rpms 4th /5th gears somtimes 3rd hard acceleration. Have checked fuel pressure/quanity. Everthing else seems fine, no codes. Changed mass airflow meter seems to good away for a 4/6 hrs running then comes back. Any ideas. non stock air box.

Geoffrey

What tests did you do to determine the mass airflow sensor? Have you plugged in the Porsche System Tester and run through the test? Have you considered a failing coil on one of the cylinders?

2fas4u

Prolly the plugs what kind are you using, fr6's are the best. If using fr6's then coil packs are suspect jmo.

Ed Newman

ETHANOL!!! My 03 996 X51 trips a check engine light for detonation with Exxon, Mobil or Sunoco 93 octane now that we have the 10% ethanol. It ran fine on Ultra 94 which is no longer available. Now I run it on Sunoco GT100.

Mfletch

Ernie. I experienced a severe surge or misfire with my non egas 99 996. It was due to my first generation EVO CAI. I switched to the stock air box and it went away. I upgraded to the second generation EVO CAI and I have no more problems.

Ernie J

Thanks Mark, I changed air boxes, and problem went away. Location of the mass air flow meter seems the issue.