Quote:
Originally Posted by WorldClassAccident
I know - weird.
Previously I thought I might have possibly lifted early but on the last three runs I did not lift my foot at all until over 90mph but each time there was the wobble on the revs.
In my Merc the engine management kills the revs if there is wheel spin but I doubt the BMW is that sophisticated - or powerful enough to spin the wheels at 80mph despite my modifications.
It is after the gear change, so perhaps the new higher ratio forces the drop? Auto box remember - might be relevent
Any thoughts or theories welcome. It is bugging me now.
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IIRC from your videos it happens in all your tests including those before you cleaned the MAF and fitted the new filter, so they're probably not the cause.
It seems to happen only in third gear, and you're running WOT in all the tests, so it appears to be related to velocity rather than engine speed or loading.
You haven't got a flux capacitor and it's unlikely to be caused by the red-painted engine cover. I was kidding when I suggested it could be the traction control kicking in, and you probably haven't got ESP in any case.
I googled it on your behalf and found only one hit-
http://forum.roadfly.com/threads/2219845-325i-flat-spot but at least you're not alone.
Switch your auto gearbox to its other modes and try again (and video it for our edification) to see if it's only happening in sport mode. Does your test track offer sufficient length to accelerate from 4000 to 5000rpm in fourth gear - unless that's ridiculously fast (don't video this one!).
Does it happen at partial throttle settings? Worth trying this again at 4500-4800 in third at partial, steady throttle, as well as accelerating throughout the rev range looking for flat spots. Or you could just ignore the problem and enjoy driving your good looking, good sounding car.