Hello forum members,
I'm obviously new to this amazing forum. I came across a 6-year-old post discussing a problem that I've been suffering from for almost a year! So I decided I should be part of such knowledge base.
I am a Mechatronics Engineer with an MSc. in Artificial Intelligence and control theory, specialized in Autonomous driving. I am currently employed by one of the top notch automotive tier 1 suppliers for sensors and ECUs.
I have always been a bimmer fan as a child, until my father bought a W210 E200. I was in love with the thing! It totally changed my mindset, given its luxury, while still maintaining its amazing durability. For my first car, I got an Opel Astra J, which I kept for 2 years, and sold it right after the auto transmission died. I hated it, and decided to invest in a benz. I found a W203 C200K in mint condition with 90k km on the clock. It had the same m111 engine that was in my father's W210, and which I loved, but with the additional power and agility because of the compressor. I bought the car and have been enjoying it ever since. EXCEPT for this stupid noise that I can't seem to solve.
This has started happening after a head gasket job. I have been studying the design of this engine carefully. A possible cause would be that whoever installed the timing chain back didn't ensure that the intake cam adjuster was at the fully retarded position. This would cause the intake cam to be always more advanced than it should, which would in turn increase overlap, and increase dynamic compression ratio.
Increasing overlap between intake and exhaust valve opening events would cause an increase in fuel consumption, a louder (and better) sounding exhaust, and with high octane fuel can cause an increase in low end torque. Increasing dynamic compression ratio would cause this pinging sound when the engine is under load at low rpm when the cam adjuster is signaled by the ECU to advance intake cam timing. The pinging sound disappears at higher rpm when the cam adjuster is commanded back to the retarded position.
I hope my explanation was clear enough. Let me know if you have any conclusions.
I am glad to be part of this forum. I hope I could provide assistance to anyone with software or electronics issues in their Sterns