RE: <E30> Poor Idle Question (long)

["Fadeev, Alex" <Alex.Fadeev@xxxxxxxxxxxxxx>]

> 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

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 (everything
OK), but it the engine light will still blink it out. If the code = 1222
"Lambda Control 1", have the 02 sensor replaced. 

> My next move was going to be to check the compression to see if I hosed up
the
> head gasket and had leakage between cylinders.  I would think this would
show
> up in the cold idle though and am a little perplexed. 
> Anyone have any ideas on what else I should check?

Try the simple things first.

good luck,
alex

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