Rattling under load, fluctuating idle (archive)

I'm trying to fix a recurring problem on my '95 525i. The engine rattles under load, especially when going uphill at RPMs less than 3000. Occasionally the idle will fluctuate when coasting to a stop, between 500 and 700 RPM. Also, the car feels somewhat sluggish, especially when the idle problem is occuring. Finally, the exhaust often smells of sulfur when the car is driven hard. The car has 45,000 miles on it, and has a manual transmission.

In trying to fix the problem, I've done the following to the car:

Replaced the spark plugs.
Replaced the engine coils.
Had the fuel injectors cleaned.
Replaced the idle control valve.

I've also tried replacing the DME. That fixed the problem for two days, after which it returned, as bad as ever, so I swapped back in the old DME. That was especially frustrating, as I thought I'd finally tracked down the problem.

I'm thinking about replacing the O2 sensor next, though the local BMW dealership tested mine and claimed it wasn't causing the problem. Other possibilities I'm considering: the air flow sensor or the knock sensor.

Any ideas out there? Anyone have the same problem and fix it?

Follow Ups:

Re: Rattling under load, fluctuating idle Mark J 21:28 8/12/2001 (2)
- Re: Rattling under load, fluctuating idle Jess G. 00:35 8/13/2001 (1)
  - Try driving slower car for 2 days then go back :) Mark J 00:50 8/13/2001 (0)
Re: Rattling under load, fluctuating idle Wayne 18:25 8/12/2001 (0)

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