Crazy idling e36 (not just the surging)

[stefan15]

Hey,
So I have a new alternator, and have changed out the idle control valve. Odd thing is, the car has a wildly surging idle whenever I'm rolling and in neutral.. anyone know why that is?

Also, when I crank my fan, the headlights usually go dim. But it's a new alternator (standard one though, Bosch 80 amp for 95 325i). Any ideas?

[maxboost_R]

Is the alternator new or a remanufactured one? How old is the battery?

[three.eighteen.]

o2 sensor will cause surging

[stefan15]

O2 sensor is new, battery is fine, and I believe the alternator is remanufactured--since for this age, aren't they all?

[Nav13]

mine does that to. if im coming to a lite the rpm's will come down and it will surge a lil. It will go up and down a couple times and then its contant. whats causes this?

[el_fefes]

Ignition coils?

[djayz]

If you guys are driving automatics its the engine downshifting that causes the surging of rpms when coming to a stop.

The dimming of headlights/lights inside the car when you turn your fan on is normal especially when your stopped at lights. The alternator is meant to handle everything in the car beind on at the same time. So full fan,ac,defrost,hazards. If you want to test your alternator turn your car on get it up to normal operating temp then turn on everything that uses up power...your idle rpms might drop quite a bit but as long as the car doesnt die its good.

[stefan15]

It's a 5sp. Ignition coils can cause this? Any test I can do?

djayz:
How about long term wear? The car certainly doesn't die, but do you think I am putting abnormally high stress on my alternator? I'm just concerned about that. I get the feeling 80amps just isn't enough. Did BMW underspec this?

Either way, if it isn't a problem, I'd still like to know what causes it since I find it incredibly odd. Why is it *mostly* when I'm rolling? Despite being present at neutral, though not as prevalent.

[djayz]

It could be long term wear or maybe some of your grounds to the chasis are rusting up a little. Once a year i wd-40 and grease all the grounds in my car just to keep them clean.

Most manufacturers dont under spec their alternators or they would have a bunch of cars dieing all over the place. Specially when people use high drain devices like heated seats or car stereos in.

I have an automatic and i usually put it into neutral when coming to stop and i notice sometimes that the rpm does take a while to get to idle even after im stopped. A mechanic told me that my iacv was dirty so i cleaned that and it helped a little. Another told me to clean the TB cuz it maybe sticking and another told me to get a new throttle cable. So i guess there is different factors on the surges but my best advice would be to clean all around the TB and make sure everything is running smoothly. WD-40 all the springs and moving parts then wipe clean and lube them up with a proper grease and see how that goes.

[stefan15]

Thanks djayz, I'll give it a try and report back.