Aviato wrote I had the same exact sound and couldn't get it to go away, this sound was really noticeable when the engine got to operating temperature, always around 2-2.5k rpm. Driving uphills would cause this sound too. It drove me crazy & was embarrassing. I thought an exhaust clamp was loose but the mechanic confirmed that they were all secure. I replaced the Rod Bearings for overall peace of mind and hoping the sound would go away, but the sound was still there. Then a few codes popped up all pointing towards replacing the low-pressure fuel sensor. Replaced the LPS and the sound has completely gone away in addition to smoother idling after a cold start. I became very aware and familiar with this sound, it was easy to pick up the patterns of when this sound could be expected. After changing out the LPS (real quick job under 30 mins) all of the situations that would usually trigger this sound no longer triggered the sound! It's been about 3 weeks now and I haven't heard the sound and I have fallen in love with my m3 all over again. Changing the LPS fixed this for me.
post #42
http://www.m3post.com/forums/showthread.php?t=694148&page=2 I read this member talking about his "engine detonating when hot" & how changing the LPS fixed everything.
Adding to the discussion: changing the Low Pressure Fuel Sensor (part # 13537614317) did
NOT cure the knocking, at least in my case.
I have the same knocking sound described by everyone - easily replicated in high-gear/lower RPM situations when loading the engine, both on the street and the highway. And like many owners, my car has never threw a code. Mike Benvo said most S65 M3s he's come across do this to a certain extent, some more so than others, and mine is one of the worst case he's seen. He took a phone clip once, just driving down the street leaving the DCT in D mode which upshifts sooner in lower RPM range, and it was knocking like a mini machine gun.
Over the years I have tried putting in new plugs (at least twice) and new coils, each attempt would alleviate the symptom, but not completely solve it. Then the knocking would return and progressively get worse again; I can also feel the engine would become less refined during harder/WOT pulls. This happened on both stock ECU mapping as well as BPM's Stage 1 software.
My fix (for now, anyway) is I took Benvo's offer and let him further adjusted the timing a little bit. I'm no engine expert so don't know exactly what he did, but so far the revised ECU mapping has worked very well, almost 99.9% knock free, and the engine is butter smooth once again through most of the rev ranges I travel in (<7K).
Will continue to troubleshoot this though. Next up is to replace the O2 sensors. If I ever find a fix will report back.
