Spark Plug Coming Loose?

[Timp]

My 325E has been getting poor mileage lately, and has had issues with idling. So, I purchased a new set of spark plugs recently (turns out I got the wrong NGK's for my wires), and I noticed that my first spark plug was so loose I could have just taken it out by hand quite easily. After noticing this, I re-tightened all of my spark plugs to 20 ft/lbs and noticed that this fixed my erratic idle issue! My car idled around 650 RPM's - only bouncing very very minimally. Only the first cylinder seemed to have the super-loose spark plug.

While driving, the power felt greater too. I still have a bit of a dead spot in what feels most prevalent in 2nd gear at 2K RPM, but that is for another day.

On my way back from a friend's house, I decided to test out this power and I let the horses run at a few stop lights. After the third time of really pushing the car, I noticed my idle returned to the same bouncy 900 - 1K RPM. This was frustrating of course.

I haven't checked under the hood, since it's going to be quite hot, but is this normal behavior for spark plugs? To loosen themselves? From what I'm reading elsewhere on the internet it appears to be in some cases, but I couldn't find anything for E30's specifically. I'm going to check again in the morning, but I wanted to ask anyway.

Also, while I'm in here, I suspect one of my rear wheel bearings is out. It's very difficult for me to tell which side it is since the groan/growl is only really prevalent above 35 mph and turning left or right doesn't seem to make a discernable difference. Since I have an open differential, could I just follow the steps that this guy suggests?

Thanks everyone.

[blueapplesoda]

Put anti-seize on the plug threads and tighten them a bit more. On new plugs, I usually tighten them hand tight, then turn them 3/4 of a turn (less on plugs that have previously been installed), or whatever the angle was on the NGK package. Something closer to 35 lbs, but I 'feel' them by hand when tightening. Spark plugs have a gasket ring that gets crushed when you first install them, and if not crushed all the way, the plug will eventually work themselves loose.

[jlevie]

NGK plugs come with ferrules on the plugs. Unscrew those to expose the threaded post. If properly tightened plugs won't loosen unless the threaded in the head have been damaged.