Several times in the last week my 2005 Q45 has quit running when cruising along in town. It starts up right away again but won't rev beyond about 3200 rpm, revs oscillate between about 2800-3200 rpm with the accelerator on the floor. It seems to lose ignition and if the revs are low it won't catch itself before stalling, if the revs are higher it just feels like a 'miss': if I watch the tach it will suddenly drop and then pick up again. It is rough when trying to accelerate when this is happening. Then it clears right up and there is no problem. The check engine light does not come on during these episodes. It is very sudden so it doesn't feel like a fueling problem. Any ideas???

Despite the check engine light not coming on, I'd try to get any pending codes read.
In the absence of any codes, then the camshaft or crankshaft sensor would be a good place to start, in my opinion. The 2 sensors are the same, I would switch them to see if the behavior changes, but it seems like the crankshaft one is going out so replacing it wouldn't be exactly irresponsible. Preventive maintenance, if you may.
https://forums.nicoclub.com/02-q45-stal ... 21497.html

Thanks Ed...helpful as usual. I'll see if it's throwing any codes as a first step.

Ditto on the camshaft/crankshaft sensor recommendation. That sounds exactly how my wife's old G35 behaved when one of those sensors failed. It was also a bit harder to start. Hers threw a CEL and "VDC Off" light though.

As suggested by the posters above it threw a 335 code for the crank sensor...thanks guys...part is on the way.