RE: <E30> Poor Idle Question

[Richard Nott <gis@xxxxxxxxxxxxxxxx>]

> > Here are the symptoms:
> > 1. Cold - idle seems OK. Maybe a miss now and then, but hard to tell

> > 2. As engine warms up, the idle develops a rhythmic lope
> > which seems worse when the engine is at normal operating temperature


My E28 535 did exactly the same thing.   Cure was 'correct' Bosch spark
plugs and increasing the valve gap from 12 thou to 13 thou warm.
Replacing the O2 Sensor with new unit made no difference
(in your case it may), but disconnecting the 02 Sensor did stop the
rough idle.
This is not the way to fix it properly, use the tips above.

> The difference between cold and warm idle is that when the engine
warms up
> the 02 sensor kicks in. If the sensor is dead (easy to check - see
Bentley),
> it will cause all of your symptoms.
>
> > 4. If the engine is allowed to idle hot for a couple of
> > minutes, the check engine light comes on. The light will go
> > out if the engine rpm is brought above 1200 or so for a second.
> > If I turn off the engine with the light on and turn the ignition
> > back on, no code is displayed.
>
> The "5 open throttle test" method should result in a fault code
> (http://cbsgi1.bu.edu/bmw/repair.html). The code could be 1444
(everyth
> OK), but it the engine light will still blink it out. If the code =
1222
> "Lambda Control 1", have the 02 sensor replaced.

Cheers,
Richard
74 3.0S (Since New!)
86 535i
This info and more at:  Richard Nott's BMW Database:
http://www.gis.nsw.gov.au/staff/rnott/bmw/bmw.html

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