318i surges at low rpms

[timothy100]

My girlfriend just got an 85 318i and it surges from idle to around 2500 rpms or so. It is a lot more noticable going up hills. In the higher rpms it runs perfectly, plenty of power and no surging at all. Any idea what the problem could be?

The idle is also fluctuating from 1000 to 1500 but I think it is unrelated.

Any help would be greatly appreciated!

[James Crivellone]

Vacuum Leak, Or the common ICV failure.


Clean the ICV (Idle Control Valve) out with some carb cleaner or replace it.

[bimmer8604]

you took the words out of my mouth James,

sounds def. like a Vacuum leak.

Kyle

[KenC]

I have an M10 as well and I fixed the same problem with a "new" fuel pressure regulator from an M20.

[timothy100]

Thanks for the suggestions. I will clean the ICV today and see if that helps. Any other possibilities?

[timothy100]

Tested the ICV and fuel pressure regulator and they both work fine. No vacuum leaks either. Any other suggestions?

[DaN]

How did you test the ICV? If there are no vacuum leaks, and you tried cleaning it then, get another icv.

[timothy100]

I disconnected the ICV with the car running and the rpms jumped up to about 2000. I also disconnected the ICV and hooked up 12v to it and watched the valve inside open and close with the voltage applied/removed.

[bimmer8604]

it could be ignition related. i cant remember if you were the one who just got done replacing the distributer,rotor,coil, and stuff like that, but i would also check your ignition system. Take the cap off of your distributer and check for carbon build up, or a cracked cap. Just make sure everythiing is there and clean. You might also want to check your spark plugs, just take them out, and make sure they look okay and properly gapped. Also, take a look at your coil, and if you have one use an ohmmeter to check.

hth
kyle

[DaN]

I disconnected the ICV with the car running and the rpms jumped up to about 2000. I also disconnected the ICV and hooked up 12v to it and watched the valve inside open and close with the voltage applied/removed.

That doesn't mean that the valve is operating correctly. I would get another.

[cowden_12]

Im so glad there another thread on this. I am the one that replaced the cap, rotor, plugs, coil, TPS. Mines goin to the shop. I will be sure to update.