1985 745t

For a few months now my brick has had trouble starting after a long sit. The problem is ONLY when the car has been sitting for awhile, like overnight or in a garage.

In the past (winter/spring) the problem was a brief moment of rough running as it came up to speed, and a slight loss of power when I first got going (I have to overgas it a little to maintain power). However, the problem is generally much worse if the vehicle has been sitting in the sun for awhile, and it has become exacerbated as summer approaches.

I've done some poking around and have come across posts and FAQ pieces indicating it may be a Hall Effect Sensor. However, the car has never actually failed to start and will ALWAYS get going even under the worst of situations (all the posts indicate an actual start failure as a symptom).

I've also been thinking it might be a sign of a weak/dying AMM. I had some trouble with my AMM previously, and had to reseat the wire to "reset" it and get it running properly again (turbo wouldn't work when it was malfunctioning). I haven't had the problem again, but could a dying AMM give me these kinds of issues?

Any thoughts anyone has are greatly appreciated. The problem doesn't seem to be getting worse very quickly, but I'm concerned it may be a harbinger of a future failure and do NOT want to get stuck on the road in the middle of a 200 mile trip (I travel a lot).

Thanks in advance.

-rt