[Daniel320iE92]

So I have a 2008 320i E92 manual. Owned it a couple of months and used to drive perfectly and around June I got my first check engine light. Turned out to be issues with pre cat O2 sensors, So i bought Bosch sensors and had them replaced. Fuel efficiency was getting worse and worse before changing them, and after it was back to normal for a couple of days and then it got worse. I am currently getting low to mid 20s mpg. There was a couple of days it was around 19mpg. At the start I used to get mid 30s. It's misfired 3 times quite badly since i owned it. Now if the car is in low RPM and i put my foot down it becomes hesitant and stutters a bit. once it gets past 2500 rpm its very responsive and nice. I changed the oil solenoid too as that could have been the cause but issue is still there more so when engine is colder and sometimes I would get low oil light, but the oil levels would be perfect (I had it serviced about 5 months ago so oil level and spark plugs should be perfect) The mechanic also ran tests on the timing chain and it's looking good. He currently doesn't really knows what it can be and neither do I. I do not want to sell the car. Any ideas what it could be?

[therealdb1]

Do you have any fault codes?

What spark plugs were fitted? These motors can be quite fussy!

[Saif2018]

Originally Posted by Daniel320iE92

So I have a 2008 320i E92 manual. Owned it a couple of months and used to drive perfectly and around June I got my first check engine light. Turned out to be issues with pre cat O2 sensors, So i bought Bosch sensors and had them replaced. Fuel efficiency was getting worse and worse before changing them, and after it was back to normal for a couple of days and then it got worse. I am currently getting low to mid 20s mpg. There was a couple of days it was around 19mpg. At the start I used to get mid 30s. It's misfired 3 times quite badly since i owned it. Now if the car is in low RPM and i put my foot down it becomes hesitant and stutters a bit. once it gets past 2500 rpm its very responsive and nice. I changed the oil solenoid too as that could have been the cause but issue is still there more so when engine is colder and sometimes I would get low oil light, but the oil levels would be perfect (I had it serviced about 5 months ago so oil level and spark plugs should be perfect) The mechanic also ran tests on the timing chain and it's looking good. He currently doesn't really knows what it can be and neither do I. I do not want to sell the car. Any ideas what it could be?

You need to find out which cylinders are misfiring first,

Your mechanic should have done this by reading codes and swapping plugs/coils round to see of the misfire follows.

Misfires are commonly caused by plugs/coils or injectors.