So I have a 2004 S40 with the 1.9L Turbo engine at 168,000 miles and it seems like there's a couple issues, but I don't know exactly what's happening.

When I drive the car after it's been sitting for a while, like all day or overnight, it has a couple weird tendencies. If I start the car in the morning, I usually have to reverse out and then drive away. When I'm done reversing and switch to drive, the car lurches forward just slightly, but with an energy very easy to feel and it's definitely there. Even with the brake depressed, it happens. Once I let off the brake to move forward, it moves forward very easily and with an eagerness that I don't see any other time. I'm not 100% sure of this, but this problem appeared after one specific event. I was parked for a short while, maybe about 45 minutes or so, and near the end, I started the car and I don't remember exactly what I did, either shifted into reverse before the car stopped moving forward, or shifted into drive before the car stopped moving backward. This was all over the span of like 5 seconds max and at the slowest crawl speeds possible, but it still happened. At the time, I didn't feel or hear any grinding, just realized what I did and quickly fixed it and went home. Now, during driving, when the gears shift as the speed increases and I give gas, each shift jolts the car a little bit, just a bit more than it should, with one of the shifts more jolty than the others, but I don't know which one.

Also after a night or day of being parked, the brakes don't seem to function well enough. Around the first 10 minutes of driving, even at neighborhood speeds, stopping for a stop sign is problematic because I have to press really hard for the brakes to work. In my about 3 years of driving, I've never encountered a car who's brake pedal I've bottomed out. But for this one, I literally feel the pedal not going any further, and the car continues inching forward, frequently into the stop sign intersection into traffic. I've never let it get too far in due to preemptive braking, but it's really annoying and slightly scary. The rest of the time, it seems to work fine. I've driven minivans who could stop in a shorter distance at higher speeds with a firm use of the brakes, even slamming them. This car can't stop immediately while creeping up to a stop sign with the pedal bottomed out.and I don't think that's supposed to happen.

Could the first thing be related to my ****-up? Could it be fluid related? Or is it just old age?

Could the second thing be just that the brakes are worn out and need replacing? Is it a fluid problem? Or something more serious since it works better after the car's been driven a little?

Thanks.

 

your brake problem sounds like the vacuum pump or related hoses. the S40s have a vacuum pump to build up the vacuum at first start up, then the engine vacuum takes over after a short bit of driving and some revs. When there's a problem with the hoses or the pump, you have no power boost on a cold start so it'll take extra pedal effort.

As to the shifting, have you checked the transmission fluid level and color? may be time for a drain/fill and a check for the correct level. These cars are also sensitive to PNP switches getting dirty. You can try the "shifter row" (park to lo to park 20x fast) to see if that helps make cleaner contacts when changing from reverse to drive.

 

+1 brake vacuum pump.

Also, check your motor mounts. If the bottom 2 crack it can cause the engine to rock back and forth excessively. On my 2001 I noticed it mostly with the car stopped, in gear, with my foot on the brake the car would shake excessively.

A quick visual test is to open the hood and have a helper start the car and place it in gear with their foot on the brake. The engine will move slightly. If it moves a great deal then you want to inspect the bottom 2 mounts with the car up on jack stands. If you find the rubber cracked then replace them. They are not too expensive and replacement is fairly easy.

 

I was going to preemptively replace the ignition coils and the fuses because of an engine misfire code on May 7, but before I ordered any parts, I was trying to look at the condition of the wires for the coils to see if I needed to replace those, but I don't have the tools. I drove around to a local mechanic and asked him if I could borrow a torx bit to open my engine cover, but when we opened it, the coils were already replaced and the wires were new as well. The coils were black and blank, no brand on them. They were replaced by the previous owner. He then pointed 2 cars away and lo and behold, there was a perfectly nice looking 2001 S40 with the same engine, just lower trim level with less options. He told me that was his and he just cleaned it up and fixed the same problem I was having with the brake vacuum. He sold it and is waiting on the buyer to come get it.

His assistant came over and removed the hard, broken o-ring out and put in a new one with some NAPA lube and put the cable back in. The brakes are fine now, but the car still lurches forward when shifting into drive after a cold start. Turns out, I just need to let the car warm up before driving it because it idles high at 1000RPM when cold. He charged me 40 bucks which isn't too bad I guess, but at least now I know how to fix it if I need to.