Engine races

July 25, 2007

2005 Impreza 2.5 ? five speed standard

When the engine is cold and I move the car in reverse, it frequently races to 2000 or sometimes 3000 rpm?s for several seconds. My foot doesn?t have to be on the gas pedal for this to occur. The increase in engine speed happens when I touch the brake to stop the car.

For instance when I back the car out of my garage in the morning (on the level) I will put the car in reverse, release the clutch and let the idle speed move the car backwards (MY FOOT IS NOT ON THE GAS PEDAL AT THIS TIME). After the car is out of the garage, I will then depress the clutch and apply the brakes (MY FOOT IS STILL NOT ON THE GAS PEDAL) – when I apply the brakes, the engine increases in speed.

The condition is more prevalent if I do this on a steep grade (front of the car facing uphill). Also, is seems to be worse in the wintertime when it is really cold. Also in the wintertime, in addition to racing at start-up, the engine will race between gearshift changes. After a few minutes when the engine gets warmer, all these symptoms stop.

I have tried tapping the accelerator as I back out of the garage, hoping that might eliminate the problem ? it does not. Also, the engine must be completely cold for this phenomenon to occur. In warmer weather the car must be parked many hours until the engine cools before the problem returns. In the winter when it is cold outside and the engine can ?cool down? quickly, the problem will return. The problem however is not consistent ? it might not happen for several days and then suddenly start again.

Though the problem mostly occurs when the car is faced uphill, it sometimes occurs when the car is faced downhill.

I?ve had the car checked several times at the Subaru dealer where I bought it. They can not find the problem. They even checked with Subaru Of America for advice or any download updates to the engine computer that might solve the problem. It appears there is no (known) solution to this problem.

Do you have any idea what might be the cause of the problem?

Sounds like it could be your vacuum assist to the break master cylinder. What perplexes me is that the cold weather is affecting it.