I seemed to be having some problems with my 2004 996 turbo convertible when cold the engine tries to cut off as i brake. It’s not necessarily hard braking even moderate braking drops the RPM and then the engine kicks back again. It seems to go away after 20 minutes of driving.

I check with the specialists and they can’t find anything wrong with it. They’ve suggested that i clean the throttle body and the oxygen sensor. This was done in the last service and it went away for a while and then it just came back again. The same thing happens with and without the A/c

I’m thinking it’s a vacuum leak but why does it go away after a while?

This started recently after I had the diverter valve changed as due to a leak the turbo was unable to kick in. Could it have been something they did then?

Incubus

 

Probably need to leak test the system. I suspect they left a hose off or something else is leaking.

 

I had exact same problem.

I've been on a track this saturday (small track, revving high in second most of the track for 7 hours - 6 laps at a time). No sign of the problem since then. I have no idea what happened and it's really interesting.

I used same fuel on track as I do daily.

 

Some say its the fuel pimp ... split fuel lines .... I have the same issues ... a rarity on my end though.

 

oh, I meant fuel PUMP LOL

 

Becuase when the engine is warm the DME is running in a different 'mode'...and isn't susceptible to the vacuum leak...when cold it is enough to cause the issue... ?

A