So I took my '94 525/5 into a BMW shop to have the state inspection done and also had them look at a few things the previous mechanic's owner told me to have checked out. (all of which were fine, which is awesome)

Anyway, I asked them about what I thought was a rough idle when it's sitting at 600 RPM and also the fact that the idle is rough between 2K and 2.5K...

They said the idle wasn't bad and checked the computer and there weren't any codes, etc. I also think the exhaust smells a little gassy.

BUT...I don't know how these cars are SUPPOSED to idle/smell/etc.

One thing I noticed today is that the idle oscillates slightly, which makes me think something might be sticking???

It has new plugs, a new air filter, the injectors were serviced, and I'm also running some Techron through the system and will repeat at the next tank, followed by an oil change to either Amsoil or Mobil1...not sure what weight I'll choose.

Anyway, someone set my expectations...I'm used to driving my 2001 Maxima, which purred like a kitten...Of course, it doesn't drive as well as the E34. ;)

Thanks!

hmm, the smell could be attributed to catalytic converters - if they're on the way out. Roughness in 2-2.5k RPM range could be caused by corroded ground connections.

Another related or unrelated note...I've noticed that there is an increase in power at around 3K RPM and 5K RPM. It's almost as though a turbo kicks in. For instance...If I start out from a corner in second gear and am initially at around 2K RPM and hold the pedal steady as I accelerate, the car gets a boost of power at 3K and 5K. I'm thinking it's one of three things:

1) There's something hurting the power at the lower RPMs.
2) It's been chipped.
3) It has a turbo.

So, #3 is probably definitely not the case. #2 is a possibility, but I'm not sure if that's what a chip will do. #1 is the most probable and I'm wondering...Is that how it would act if the ground was bad and if so, how do I fix the grounds? In the front of the engine compartment on the driver's side there are several wires coming together and are attached to the frame...Is that the only grounds I need to worry about? Does it matter what I clean them with?

solution - VANOS ;)

BMW's own funk-nasty brand of 'VTEC'.

at least i'm pretty sure your '94 525i oughta have it. my '93 325is had it @3.5k, 4.5k, and i'm pretty sure it also had it @5.5k.

i don't see why your 92+ model 2.5L I6 shouldn't have VANOS ? anybody ?

that's probably what it is. pretty much your BMW is VTEC powered. yay!!

variable valve timing r0x my s0x.:buttrock :buttrock :buttrock :buttrock

-Andrew-

Yeah, my engine has VANOS.

So, the variable power is a "feature", eh?

Interesting...

Try cleaning the idle control valve, it controls the air into the motor at idle, and after time it tends to gunk up. Pull it off and blast the insides with carb cleaner from both sides until the little flap on the inside moves freely. Don't worry, it will make sense when you see it. Not sure where it is on the 6 though, on the M60 it's right above the throttle body, connected between the intake elbow and the intake. Clean the electrical connections too, after I did mine I didn't clean the contacts, and had a rough idle until I did.

Another hint, www.bimmerinfo.com is an excellent source for the E34, probably better tech info on there than on BF.

hmm, the smell could be attributed to catalytic converters - if they're on the way out. Roughness in 2-2.5k RPM range could be caused by corroded ground connections.

Today I left work and the throttle was oscillating again. This time, I had my lights and fogs on and it caused them to dim then increase then dim, etc. I turned my fogs off and the oscillation stopped, though it was not idling 100% smoothly. Does this throw more fuel on the possibility that a bad ground could be a problem or is it just saying that my battery/alternator may be going?

I should note that after a few minutes of driving it didn't make a difference whether my fogs were on or off, the car idled fine.