I am hoping to get help diagnosing a current problem I am having with my 2008 335i from someone who may have had a similar issue. I upgraded to this car a few months ago from a e46 323ci so I still have a lot to learn on the e90s. Tonight I was pulling out from a stop sign and the half engine yellow light came on, shortly followed by the upper yellow "check engine soon" light. The radiator fan then started blowing at full speed, but I never smelled coolant. I raised the hood with it running and didn't hear anything abnormal besides the fan. I was a couple miles from home, so I limped it back to get my OBD2 reader. The whole way it was jerking and surging, especially below 2500 RPM. The code reader found 3 codes, but just displayed them as "N/A". I will try to borrow a better reader from a friend, but in the mean time trying to find some answers. I erased the codes and restarted the car and both lights immediately came back on. Any suggestions/advice would be greatly appreciated!
You need to codes but it sounds like your thermostat. The thermostat stays open until the engine begins to warm up. When the temperature delta gets high enough, the thermostat shifts. If that shift doesn't happen, the fan goes to full blast to ensure sufficient cooling. I hope this helps and gives you some direction. Cheers!
The car is going into overheat protection mode thats the fan kicking on high. Your water pump will need to be replaced you should have coolant pump speed deviation faults to confirm this. Yes also replace you thermostat while doing this job since it has to come out any way. As for the bucking you might have a misfire issue going on would need codes to confirm that but most the time its because of the poorly designed injectors. Just look for the index number on the injectors if its less that 11 they should be replaced. Lets us know what you find out.
