Alright I have two issues.
First is my mom's 2004 BMW 525. When accelerating, the RPMs move up and down very inconsistently. Overall, the car seems to accelerate fine, but the car is slightly jerky due to the quick and small changes in RPMs. It's acting like you're quickly pushing and letting off of the gas pedal, but in fact you're holding it steady. I've only driven it around town on very short trips so I'm not sure if it gets better as the car warms up. Perhaps a faulty or dirty mass air flow sensor?
The next problem I'm having is with my 2003 Nissan Pathfinder. The brakes make a high pitched noise when slowing down at times, but I had it looked at shortly after I purchased the vehicle (I bought it this past November) and they said that it was temporary and would subside after driving it around a bit. Perhaps I need to get them cleaned? Sort of the same issue with the serpentine belts--they make a squeaking noise, especially on cold and/or rainy days. Is there some kind of spray I can use to fix this temporarily?