Just wanted to post this potential fix in case it can help someone searching for it later...

My 2010 997.2S (manual transmission) had 4 episodes of stalling when coming off throttle.
Twice were in the mornings when the car was cold, at the stop sign 100 yards from my house. Those were annoying but no big deal.

Then I got two more stalls while in traffic at 40mph, in 4th gear slowing down for a turn into a store's parking lot. Clutch in, shift into 2nd and no revs. Engine died, along with power steering and brakes. That was exciting.

The car restarted no problem and I didn't have any check engine lights. Took it to the dealer and they couldn't find any error codes. They said potentially it was a crank sensor or throttle body servo failing, but that they'd really just be throwing parts at the problem without more data, and they couldn't replicate a stall.

I decided to start with the simple fixes and bought a can of MAF cleaner. (I used to have a 996, where all problems that aren't IMSs are usually the MAF sensor. Took the intake hoses off and sure enough... the throttle body had a nice caking of carbon, with a noticeable black lip of the stuff on the inside of the TB. Cleaned the TB and the MAF while I was at it and three weeks later I haven't had a stalling episode since, and the car's got a smoother idle to boot.

So is your 997.2 stalling with no check engine lights? Start off with a $5 can of MAF sensor cleaner.

 

Thanks for the info !

 

yes, thank you...I just love easy DIY fixes

 

Nice reminder OP! I was doing my neighbors 4S' belt a week ago, and found the same thing and also addressed it. Pretty typical for a bit of oil residue at the butterfly on these 3.8's.... Particularly if running a kn /bmc filter type.

 

Saw this and decided to do it on my 997.1. I have no issues with it stalling, but since I changed the air filter I cleaned the throttle body and the MAF. I have to say that it made a difference in my car. Now feels like it doesn't struggle while accelerating. I would suggest if you haven't done this before, or haven't checked it in a while, give it a go and post your experience to see if it did make a difference.

 

A dirty enough to clean TB that is dirty enough to affect engine behavior and once clean improves engine behavior has in my experience been a precursor to a bad AOS.

With the stock air filter and air intake system the MAF should not ever need cleaning. I have driven hundreds of thousands of miles without any need to clean the MAF and both cars and engines run just fine.

While the engine stalling is a bit of an extreme behavior to attribute to an E-Gas system that is in need of calibrating one might consider performing an E-Gas calibration. If this hasn't been done in a "while" (I do this after every 5K mile engine oil/filter service) I'd do this anyhow. It costs nothing.

The steps should be in car's owner manual.

For my earlier model cars, the steps are with your foot off the gas pedal through out the procedure, with the engine off and the key off turn the key to the on position and leave the key at the on position for 60 seconds. After 60 seconds turn the key off and leave it off for at least 10 seconds. The next time the engine is started the E-Gas system will have been calibrated.

 

I have cleaned mine just for fun but there is also a throttle adjustment cycle you can do. Fast and easy DIY.
Search it here.

 

https://www.6speedonline.com/forums/...tle-reset.html

Found it.

 

Thanks for the heads up. The car's got about 35k on it, and the problem became worse after a hard driving weekend on the track. Lots of engine braking. Could that accelerate buildup of gunk around the TB? (The MAF really looked spotless, but I cleaned that anyway since I was there.

 

If there is build up of "gunk" around the TB that's not normal. The only thing that the intake and TB should be exposed to is filtered air with one exception.

The exception unfortunately comes from the AOS which routes crankcase fumes to the intake downstream of the TB. IF the AOS is going bad this can -- at least this is the case with other models -- route excessive oil vapor to the intake and this can foul the TB.

The real problem is not the fouled TB -- though this should probably be cleaned -- but the AOS.

Now hard driving, track driving, can exacerbate an AOS problem. Either the usage can overtax a marginal AOS or accelerate its demise.

Absent any signs of a failing AOS -- rough idle, varying idle speed, CEL, prolonged smoking upon cold start or at any other time, difficulty removing the oil tube filler cap when the engine is idling -- my WAG is your track usage just overtaxed the AOS and it passed through a goodly amount of oil vapor.