misfire 996 turbo
 

hi everyone,

just got a 04 996 turbo a couple of months ago. I started to notice car was misfiring at about 4000 rpm when gas pedal was floored. Check engine lite came on. I thought bad gas so filled up with seeming no problems for a week or so. Then today same problem. when car is in neutral revs just fine with no misfire, only when im in gear and moving. car has APR chip and exhaust. Bought the car from washington state(sea level) , live in new mexico 7000+ feet. Any suggestions or thought would really be appreciated
brooklynsav

You need to change your spark plugs. Problem will go away. Use Bosch FR6LDC

thx porscheDoc, Do you think it can be any thing else? Searching around and some people mentioned coil packs or boost leak what do you think? Only happen at WOT. Car has 33K on it. I bought after it was just went for 30K tune-up, dont they change plugs at that service?

Most shops don't change plugs until the 60k mark, which is a mistake in the twin turbo. They absolutely must be changed every 30k, sometimes more if you are running an aftermarket program which is using higher boost and fuel. If they did change the plugs and did not use an FR6LDC, then they need to go back in there and put in the correct plugs for your program.

Typically when a coil pack goes, the CEL will flash at you as it is causing a constant misfire. You can read the code down to possibly determine the cylinder it is misfiring on, but i would lean 95% towards bad plugs.

Typically a boost leak on the 996TT involves ripping an F hose, or blowing one of the intercooler hoses, and the car will not make anywhere near the boost it should.

BTW, plugs books for about 5-6 hours, so you should be able to look on your 30k service invoice and determine if they were done.

hey doc,

i got the plugs /coilpack 2 and fuel filter changed and man did it make a difference in acceleration and power! But then i noticed when the car idles it will occasionally have an uneven puff in the exhaust sound and the cars idle speed will will drop for that split puff and car shakes a bit. no CEL or anything else. at speed car drives awesome full throttle no problems like before, what do you think?