Re: Bogging E30

[alex.fadeev@xxxxxxxxxxx]

"David W. Reichel" <reichel2@domain.elided> wrote:
> My 1984 325e "bogs" on acceleration.  The motor idles fine and runs
> well during normal crusing as well as at full throttle.  Problem
> occurs when accelerating through the gears (5-speed).  The motor
> will accelerate, bog, accelerate, bog, etc. during normal takeoff.

David,
Does the bogging occur at any given RPM range?
Engine cold, warm or hot?

> If I floor it, during the bogging, no bog and the motor accelerates
> with authority.  I have replaced the air flow meter, as well as a
> complete tune up including valve adjustment.  Any advice on what
> to look at would be appreciated.

Two things come to mind:
1. The 02 sensor is dying and confusing the DME. At WOT, the 02 sensor
input is ignored (DME goes into open loop). You could try testing the 02
sensor's output our unplug it altogether. The DME would go into 'no 02
sensor' default mode and may run the car a little rich, but the car will
run fine (may throw a check engine light).
2. The idle control valve (ICV) is sticking. Don't bother testing this one
with a voltmeter. It may pass all the tests at idle and still stick on the
road. If unplugging 02 sensor does cure the bog, replace the ICV ($90 new
or $45 used).

If all else fails, suspect a flaky DME.

alex f

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