If it's still rough with the O2 sensor wire removed, look up AFM Calibration in the archives and do it. If that doesn;t make it idle smoothly, you may still have an ignition problem, or one or more injectors are not spritzing a nice pattern.

On the rpm oscillation, make sure that the TPS is closing when the throttle plate is at idle, and clicks open when the throttle is barely opened.

Bob
'87 535is Idles so smooth you almost cannot feel it in the gear shift lever.
Hi,

Have just gone through the littany of replacing tuneup parts on my 197k '87 535is. Pressure regulator, plugs, wires, cap, rotor, ICV, vacuum lines, and O2 sensor are all new. Valves have yet to be adjusted. No visible vacuum leaks, and most all the usual spots have been checked. Also checked AFM for free movement and fuses/grounds for cleanliness. Was incorrectly jumped/boost charged at a shop about a week ago, which killed the DME (thankfully, not by me, so I didn't have to pay for it), so that's new as well.

It starts fine, and idles at a constant speed (~750) until the O2 sensor comes on line/car warms up, and then starts to vary in speed, by about 100-200 rpm. Idle is somewhat rough, rocking the car a little bit. Disconnecting the sensor makes it stop wandering, and it's rock steady in terms of speed - but not smoothness. Still the same rumbliness as before.

Any thoughts? Could the valves really make this much of a difference? This is the first big six I've owned, and am not familiar w/their peculiarities yet. Do know all the common cliches, though, like "they all idle bad and last forever", etc. Refuse to believe this car cannot be made to idle. I've read the FAQ and have the Bentley.

Thanks

Sam Smith
'76 inka '02
'87 iS