After 2+ years of ownership, I've been noticing some new PDK behavior and wanted to see if others had a similar experience. On a cold start, after car has been sitting overnight, car will lurch (almost jump) forward after I shift to drive and take my foot off the brake. If I let the car sit and idle for a bit, and let the revs drop to 5-600 rpm, the clutch will engage smoothly when taking my foot off the brake. If I park and drive the car frequently the rest of the day, the clutch will engage soothly when shifting into drive. Only recent service was a PDK fluid change maybe 4-5 months ago (behavior started maybe 1 month ago).

 

A new, undesirable behaviour is generally, by definition, not normal.

I'd call your dealership or the shop who performed the service to see if they have any ideas.

 

If it is new to you, then have it checked. I would guess they say that it’s within specs but can’t hurt to have it documented as “ Customer states rough start into first gear since PDK fluid replacement.” Only issue is that you won’t be able to reproduce it since you have driven to the dealer. Maybe leave it Sunday night at the dealer lot and take foreman for a drive Monday morning?

 

Yes, that may end up happening. The dealer is far from me and I don't exactly have a lot of free time. I guess I was moreso wondering if anyone else has experienced anything similar. PDK acts normally once warmed up, both up and down shifts are rapid.

 

Are you saying: upon cold start you put the car in gear before letting the car's revs drop down from the initial cold-start warm-up cycle (i.e. injtial revs 1500-2K rpm)?

If so, I believe I e noticed this behavior as well the one time I had an emergency and tried to pull off fast upon vold start. Otherwise, never notice because I ALWAYS let the initial warm-up cycle complete (i.e. revs drop down to normal idle before putting the car in gear).

The PDK by default comes with Idle-Creep, so at higher revs would have the car in "idle-lurch/idle-jump" mode 🤷🏾‍♀️

 

Correct, only if I put in drive and take my foot off the break before I let the revs drop. If I wait until the revs drop after warm up, it takes off smoothly. I don't seem to remember this behavior before but maybe I'm mistaken.

 

Sounds somewhat normal to me.

 

Isn’t that like driving off part throttle? This seems normal to me for when engine is still in ‘start up mode’ (lack of better description).

 

Just to give some closure to this thread, this was most definitely happening due to the fact I didn't wait for the car to warm up. The last many times I've started the car, I've waited for the rpm's to drop to usual 7-800 and it has not jerked forward after shifting from park into drive.

 

On fast idle you're obviously going to get more of an impulse when first gear engages.

 

I never warm up the car. I start it and drive off. I go slow until it gets to temp.

 

Not sure why you wouldn't let the car come off cold idle before shifting it in the first place? It's only 30 seconds or so plus allows the car to warm up and get the oil circulating. With the rpms up over 1500 of course the shift will be more aggressive. Let the car warm up some before taking off. I never just jump in after letting the car sit over night and take off right away. To hard on it (any car for that matter) I always allow it to warm up some (100 degree water temp)

 

prevailing wisdom disagrees. it's more damaging and wasteful to idle the car up to a temperature than it is to drive it up to the same temperature. just drive, but keep load low (read: don't floor it out of your garage)

I have waited for a car to warm up exactly twice, and it was on a -30f day where a 20 year old high mile car was parked outside for 8 hours. I gave it about 15 seconds to get oil fully circulated, then drove off.

FWIW I do not experience the behaviour the OP has described.

 

To each his own I guess......

 

Not really. It is one of the issues that the 997.1 crowd has to deal with in terms of bore scoring. Because modern engines need to meet emissions control t requirements, they run rich when cold. It is better to start driving cold under light load, rather than letting it idle. At least that is what I learned from the experts repairing 997 engines