Loss of power on my 2001 volvo s40



i bought my used s40 last July 2009. right after i bought it, i changed air filter to k&n and replace all plugs.

It happened several times:

1st my wife reported that it lost power as she drove the car up the slope and turn to left. the gas was close to empty. solution: keep tank full and , for sure, with high octane gas. It never occured with my wife.

2nd My son just reported that, after driving the car for 4 hours in the mountain area, going down the slope, it lost power. Engine was still on. He stopped the engine and 10-15 minutes later, it worked like a charm.

Engine light was never ON.

I searched Volvo forum s40 and i found some possible problem but the thread has engine lights on: ECM- 603C and ECM 603D which are “turbo contral - pressure too low and too high”.

My question: does it make sense? what should i do with it? change turbo valve pressure?


Why would your son need power going down a slope in a mountain area? In these cases, I downshift and never touch the gas, since gravity is pulling me down at a good clip. Going up the mountain, I wouldn’t be surprised if he caused a minor overheat problem which affected the power.

IMHO, I’d never go around changing parts chasing a problem. On today’s cars, it will only lighten your wallet, not solve problems. These parts can and should be tested.


That is a very good question. I need to talk to him again in detail when he is home.


First, remove the K&N filter and go back to the stock filter. The oil from the K&N may be interfering with downstream components. If Volvo wanted you to use a K&N filter, the owner’s manual would specify one.

DO NOT mess with the turbo valve pressure. Doing so will cause you more headaches than you can imagine. If you think something is wrong with the car, take it to a Volvo specialist, preferably an independent, and let them check the car.