325E runs rough OR rolling idle
 

85 325E with approx 160k miles (don't know for sure, odometer is broken) does one of the two:

1. Idle rolls between 800 to 1300, then drops back and repeats. Annoying, but the car drives fine.

Or.....new habit

2. Idles at a near steady 800, but feels really rough. When it does this, slight smell of gas and really bad mileage (<15mpg @ 30mpg according to the economy gauge)

Also, dies without warning when it goes into non-idle rolling. Maybe once an hour, like I turned the key off.

I've worked with E36s, but motor problems are new to me. I did a search on the idle being possibly vaccumn related, but I am perplexed by the "smooth" idle at times. Can the eta engines run ok with 5 cylinders?

Ideas? Planning to give her a tune up this weekend as a bribe for good behavior.

Thanks in Advance.

Aub

85 911 Carrera - Weekend toy
85 325E - Daily driver
01 Lexus IS300 - Keeps wife happy

99% of the time, a surging idle is caused by vacuum leaks somewhere in the system.

Even with leaks, you still can have a intermittent smooth idle. As for the gas smell, that would indicate that possibly the Oxygen sensor has failed, resulting in an overall rich mixture.

Have you checked the error codes on the car? THat is a good starting point.. Look here...http://www.pelicanparts.com/bmw/techarticles/Mult-Code_Reading/Mult-Code_Reading.htm

Is there any reason why the gas smell would occur only when the idle smooths out? I can usually tell when it's happening by watching the value of the economy gauge...30mph will net 25+ when the idle rolls, 15ish when the idle is smooth. Should I check the plugs for wetness? What would cause one cylinder to stop firing, assuming this is the problem?

I hope to get my hands on a code reader soon. My friend (who is also the PO) said he would send it. But that may be a while.