Car began lurching/chugging forward as I tried to accelerate onto the highway, reminiscent of spark plug problems, except that the plugs were replaced the day before. Car slowed to "limp" mode and "reduced engine performance" light came on. Exact same thing happened exactly one week later. I took it in to the dealer and was told they couldn't find anything wrong--no codes were coming back on the computer and that it was a weather related issue. Less than one week after getting it back it did the same thing, thankfully, AFTER I crossed a major road. This time the check engine light came on, as did the "engine system service required" message. According to the dealer, the throttle control needs to be cleaned and possibly the mass airflow sensor needs to be replaced. I thought Volvo had fixed this on '02 and later. Guess not.