I have a 2002 996 911 turbo and it does not idle well at all. When the ac is turned on the car stalls sometimes too. Do any of you guys know what the problem is.

 

not enough info for an amateur to help, but rough idle is often a sign of a falling MAF. particularly if you get idle "hunting" minor rpm = up/down, but in addition or alternately, you probably have a small vacuum leak. you need to (a) test the car diagnostically with a duramteric scanner or have a shop do it, and probably even more importantly (b) have a pressure test for "leaks" done. a leak will cause idle issues for sure. good luck.

 

^^^^ This

Without any scan for codes from Durametric or even CEL it's hard to answer your question. Can you share more information? I agree that MAF or vacuum leak are possible culprits. When the MAF fails you typically see an ABS+PSM failure warning. You didn't mention this so I am guessing you didn't see it. Vacuum leaks will make your idle "hunt" but usually they will keep the idle slightly higher, not lower depending on the size of the leak.
Without a scanner, you could just pull the connector off the MAF and see if the idle gets better which might indicate if it is the reason for your idle/stalling problem. Troubleshooting vacuum leaks is a lot more involved but you can search for detailed threads that exist here for testing both.

 

^ very well put. i forgot about disconnecting the maf. that will often tell the tale.

 

I wanted to help/comment but mrmaass is correct and it will take some trouble shooting/testing to figure out. Vac leak was my first thought.

 

sounds like vacuum leak.. a hose popped off.. if its high idle...
can also be a boost hose...
you need to do a pressure test.. and a good one... and dont go to just any shop they will be lost...
get a pressure test kit.. we sell it.. find a buddy with a compressor in garage and do it in 15 min... you will find the problem.. case solved..
markski

 

Mark,
Any advantage to pressurizing from the air intake at the Maf? I've always done the pressure test by blocking one turbo inlet and pressurizing the other.

thx..

 

You can't get pre turbo sealed up well plus it will go thru into the oil via he black hose in back.
Doing it from the turbos is good but it also will go they the catch can and up into the motor and it will tought to get it to seal up due to blow by.
Best in my opinion is from lower boost hoses. You block one off and pressure the other.

 

I had this problem when I would start the car with the AC on. When the engine would still be warm (not hot), it would stall with the AC on. Once at full operating temp, it was fine. I had my mechanic check for leaks; he didn't find anything major but pulling a few things apart and tightening it all up nicely must've been sufficient. Problem went a way.

When the MAF went out, it would also idle rough and nearly die before jumping back up. That was combined with the "ABS failure" message as described above.