Troubleshooting
Unstable Idling
One day, I started having some rough Idles and shaking at many different RPM ranges. From my perspective I was very concerned as I just recently tuned the car and I thought it was a faulty tune. Through multiple challenges and troubleshooting of the tune I decided it must have been something mechanical causing this issue and went into many weeks of trying to solve this issue.
Sand Blasting and Intake Valve Cleaning
The first thing I did to was to clean the intake valves of the car. This is a common issue in Direct Engine engines because there is no system to clean the valve. In port injection, the fuel is used as a cleaner because it sprays over the valves and cleans up any carbon. In direct injection, the fuel is sprayed directly into the cylinder head, so carbon can build up on the valves as it is only air. Although direct injection is more efficient and tunable, it can still cause this issue. To solve it, first I did some intake valve cleaning using a spray cleaning and spraying it directly into the throttle body. Then, I had a shop use sandblasting, an extensive procedure where you blast sand on the intake valves to break up the carbon. Both of these cleaning procedures allow for a much smoother ride as more air can flow freely into the engine without the buildup. Although, it did not solve the main issue of the rough idle...
These are real photos of the valves on my X5's N55 engine
O2 Sensor
Finally, I was able to find the root cause using an OBD2 reader that could read the engine codes. It said the engine had a heated circuit in the post catalytic O2 sensor. At the shop Gus Auto Repair, also talked about in my Resume, I was able to use a lift on my car and get under the exhaust system to get to the catalytic convertor. This was a simple but hard to reach install as the sensor was at quite a weird angle. Looking at it there was loads of soot on it from the ECU tune's backfiring. BMW tunes often have backfiring for the sport of it, but it can cause damage to sensors, turbos, and the catalytic convertor. So, after putting in a fresh O2 sensor, I retuned the car to not have backfiring anymore.
