2003 330i zhp, 6 speed, ~185K miles, pretty healthy car overall, no lights on the dashboard.
I went to pass somebody on the highway yesterday and put the pedal to the metal flat in 6th gear. Car started to accelerate as expected from 2.5k RPM. At 3K RPM, tach needle went to 4K faster and came back to 3K on its own. Mind you, at that time the car kept accelerating at a normal rate, but I could tell that it wasn't just a weird act on behalf of tach needle - the sound of the engine also indicated that it revved up to 4K and came back down. Most importantly, car kept accelerating normally through this weird behavior. The car acts the same way in 5th, 4th and 3rd gears as far as I can tell and it seems to fall under 3-4K RPM in any gear. This really got me stumped. I really have no idea where to begin troubleshooting.
Clutch?
Was my initial thought, but clutch is disengaged throughout this "ordeal", no?
How old is the clutch, typically if you are cruising a city street type speeds in high gear accelerate quickly the rpm's go up but the car really does not. If you back out of the throttle, then it feels normal, for awhile.
Clutch is likely going bad.
Take to a BMW shop and have them drive the car, if it's slipping techs know how to induce it
Classic test is to get into 3rd gear, run up to say 3000 rpm and hold the car back with the brakes while you keep the pedal floored. If the engine rpm 'flares' then you have a slipping clutch.
The clutch can be inspected visually from below I think there's a plate or viewport or perhaps a cable/viewer can see the clutch thickness.
Besides, at 185K (and it's not an M either...they tend to last longest if you don't abuse them) it's not unlikely you need a new clutch and pressure plate and throwout bearing.
Turned out to be worn clutch along with flywheel that has excessive wobble to it and disintegrated fork pivot. Clutch disc had uneven wear due to excessive play in flywheel, but was not at critical stage yet - I am glad I caught this before it completed chewed itself up! Thanks for help!
Good catch. Glad you got it sorted.
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