[gpshumway]

Visiting my parent's over the holidays I drove my Dad's 3.6R and noticed a strange problem when the car is cold.

When stopped with the transmission in D the car surges as if the transmission is shifting in and out of gear. You can feel the car pull against the brakes, release, then the cycle repeats about once a second. I wouldn't call it a vibration as it happens at a frequency substantially below any rotational speed within the drivetrain. It only happens when cold, though I can't tell whether it might be high-idle related or cold transmission related.

The car behaves normally once the brake is released and you start moving forward. No abrupt gear engagement or slipping.

Anybody experience similar symptoms?

 

[98 Hawkeye]

Just happened last night

I had the exact same thing happen to me last night. I am thinking this has something to do with the idle. When I start my car and it has been out in the cold, it seems to excessively idle (almost as if I am pushing down on the accelerator). After 10 to 20 seconds this dies down to what I would consider a normal idle. I know that cars do seem to have an initial period where the idle is higher after just starting them but mine seems excessive when it is cold. I have been at a stop after just starting the car and I really have to apply the brake because the car wants to surge forward. Last night I experienced the same feeling that the car was surging forward in a pulsating fashion. It happened when I first started it and it stopped when I put it back into park. I don't know if something is sticking open when it is cold and then as soon as it warms up stops. I am calling the dealer on Wednesday

 

[cardoc]

Torque converter slip. As long as it only does it when its cold, don't worry with it.

You could just begin starting the car and letting it warm up before moving it. The torque converter creates the heat that warms up the fluid. When the fluid is cold, the action created within the torque converter between the pump and turbine is increased due to the higher viscosity of the fluid, especially in low temperatures. The lock up of the converter becomes slightly lower and creates the "surge" effect. It doesn't damage anything, since the turbine spin only effects the apply of the one way clutch to drive the input shaft of the transmission.

Again,this is as long as it only does it when the fluids are cold. If it goes away after driving for a few minutes or isn't there after the car sits and warms everything up, don't worry about it. If its continuous, then there may be a problem with flow within the transmission.

 

[loudsubz]

I think I have this exact issue in my 2010 3.6r as well. Scared me a bit as it was doing it a bunch today right after I started the car and drove it away, but went away after driving for 2-3 minutes or so. Should it still be doing this even in the sweltering heat we are having?