This ones a bit hard to explain but interested to know if anyone else has experienced this problem. New car, 1400 kms on the clock. Took the family out for a drive today and we were on cruise control at 60-70km/hr and without warning the rear part of the car yawed to the left making the front pull to the right. Lucky I wasnt going fast and both hands on the wheel so all in control. Initially I thought I may have driven over a slippery patch but when I kept driving it happened every 200 meters or so. I stopped the car and checked none of the tyres were flat, all fine and drove on. Then nothing. Later when I drove again the same day, same thing happened but no cruise control and on a different patch of road. Does anyone know what could be going on? I'm thinking maybe the handbrake is engaging a bit when I'm driving or an ABS malfunction(?) may be causing the sudden yaw but apart from that I cant think of anything else. I'll take it in to the dealership this week. Thanks for any help here.

 

It may a PSM malfunction. Sensors feed information to the PSM system and any one of them could have malfunctioned. Does the car behave the same way with PSM turned off? Afaik, even with PSM turned off by the driver, it is never entirely off. Give it a go.

A dealer visit is the best option. Good luck mate.

 

Thanks Haku. I'll mention that when I speak to them today. cheers

 

I recently had a slow leak in one of my rear tires. Until we could get to a gas station and refill the slack tire, the difference in tire pressure caused the traction control system to occasionally grab on that wheel and caused the car to suddenly veer a bit. The tire was repaired and everything was fine afterward.

Your symptom sounds similar...but the cause is probably different. I have heard of a few other occurrences of this behavior with no clear cause yet. The speed sensors one or more wheels could be at fault or the PSM unit itself.

 

Brought the car to the dealership today. Porsche were very helpful indeed, even gave me another 991 as a loan car. Ispain you were spot on! Seems it was a slow leak in one of the rear tyres and the PSM was over compensating for the reduced tyre size. How interesting. Anyway, they fixed the tyre free of charge. Gotta love Porsche's service! Thank both for your help too.

 

I'm glad they diagnosed the issue.

Question. Did the tpms not display a warning?

 

Sounds like a rudder trim problem.... oh wait... this is the Porsche forum not the Cessna 310 forum..

 

 

I noticed the same thing at similar speeds - yaw to the right as though hit by a crosswind - and I stiffened the suspension to see if that would help but it didn't. Members suggested that my tires were overinflated and should be run at the comfort level. I haven't done anything about it yet as I have been away from the car for 3+ weeks. Last time I drove it it was at speed and I didn't get the yawing so it might have been the road surface that caused my temporary issue originally.