erratic idle at stops
09-26-2018, 02:56 PM
#19
Could be your PCV valve. Here's a link with some good info. https://rennlist.com/forums/cayenne-...ve-repair.html
09-27-2018, 02:38 AM
#21
Instructor
Squashed motor mounts in the 955 and 957 V8's will generate a shudder that vibrates through the steering wheel and seat when decelerating from about 8mph to 4mph and the rpms will dip a bit. This can be more pronounced if there are additional issues causing the engine to run a little rougher at idle than a normal healthy vehicle. Ambiet temp, engine/underhood temperature, the gear you decelerate in and the rate of braking can all affect the strength of the shudder. It is a very peculiar aspect of the platform and it seems all affected cars will eventually develop this issue once their 2 main motor mounts squish about 1 inch. On the turbo motors it requires dropping the engine and transmission. The non-turbo V8's can get away with replacing them with the engine somewhat in situ, with the right amount of finesse, jacking of the subframe, and the correct combination of cussing shared between two or more people working on it.
09-27-2018, 09:08 AM
#22
Easiest way would be to pick up a crossbar from Harbor freight that the engine can hang from. Drop the subframe and engine crossmember to make room.
11-14-2018, 12:05 PM
#24
Intermediate
Join Date: Dec 2017
Posts: 31
Likes: 0
Received 0 Likes
on
0 Posts
I have a similar shudder/vibration and RPM dip when braking or coming to a stop. However, when I shift transmission to Neutral and then stop, no vibration, no RPM dip. Recently had transmission fluid changed at dealer. This makes me think it is transmission issue and maybe exacerbated by bad motor mounts. Is it normal for the transmission to do this? To those who have done the motor mount replacement - do the RPMs still drop but you just don't feel the vibration?