BMW launched the E90 generation 3 Series in 2005. The 335i was introduced in 2006. The E90 replaced the popular E46 as the latest, greatest 3 Series. The E90 (E92 in coupe form) is an entirely new platform and as such has its share of teething issues that usually occur the first few years that a new model is in production.
The 335i is equipped with the powerful 300-horsepower N54 3.0-litre straight six that is twin turbocharged. While the engine itself has so far proven reliable, there have been the occasional problems with the ECU cutting power to the motor. There have also been reports of oil coolers inadequately cooling the engine if the 335i is driven very aggressively in a track environment. The installation of an aftermarket oil cooler solves this problem.
Some owners of 335is that are equipped with an automatic gearbox have been reporting problems with the gearboxes lurching and hesitating when they are supposed to be shifting smoothly. This has been occurring mainly in automatic mode and not in the manual shift mode. The dealers usually download new software into the car to fix the problem. This is not a common problem.
By far the most well-known issue with the 335i is the failure of the direct injection fuel system's high pressure fuel pump (HPFP) in 2007 and 2008, though BMW says this is rare. Failure of the pump, which delivers fuel at nearly 3000-psi, can cause long cranking to start the motor, as well as making the car's computer go into "limp home mode" and cut power to the turbos. The good news is that there is an upgraded pump that the dealer installs under warranty to rectify the situation.
It should be noted that these problems have occurred in a very small percentage of cars. The majority of 335i owners have reported trouble-free driving overall. The probability of major issues with a 335i are very low, as long as the car is properly maintained and uses premium fuel.