[bmwnzer]

I wanted to share my experience concerning my e83 30sd. I've been facing two main issues: firstly, the vehicle doesn't reach the proper operating temperature while on the open highway, and secondly, there's intermittent bogging down at low rpm. Just to provide some context, the car has covered 170k kms. I've already taken several measures including removing swirl flaps, EGR, DPF, applying a tune, and installing a new glow plug module along with glow plugs (which fortunately came out with the assistance of PB Blaster).

What I've observed is that when the vehicle is under load or climbing uphill, the temperature gauge remains steady at the midway point, which is fine. However, while descending a hill or cruising on a level surface, the temperature gauge drops to a quarter of the way up. Despite having the main thermostat replaced twice – once by the previous owner and once under BMW warranty – the issue hasn't been resolved. I also tried changing the temperature sensor, but it had no effect. It's worth noting that these temperature fluctuations were happening even before the tune. After conducting further research, I decided to replace the EGR thermostat. Remarkably, this adjustment has led to the engine running at temperatures between 85-92 degrees Celsius, which I'm extremely pleased about.

I do have some concerns about potential engine wear during the period when it wasn't maintaining the correct temperature. Unfortunately, there isn't much I can do about that retroactively. I'm also curious to see how fuel economy will be impacted now that the engine is running at the correct temperature. On longer trips, it used to achieve 7.2-7.5 L/100km, while city driving resulted in figures of 8.0-8.5 L/100km.

Addressing another issue, I'm striving to resolve the sporadic bogging down at low rpm (between 1000-2000rpm), coupled with smoke during deceleration or when the foot is off the throttle. I'm considering the possibility of a vacuum-related problem, perhaps involving the wastegate not closing properly or a valve between the two turbos being open. Interestingly, this problem emerged after the tune was applied. While I'm not entirely certain, I'm contemplating replacing all 3.5x2.0 vacuum lines to determine if this rectifies the issue. I'm also interested in hearing from others who might have encountered a similar problem.