RE: Why is cable unplugged?

[alex.fadeev@xxxxxxxxxxx]

Ryan Sabir [mailto:ryan@domain.elided] wrote:
> 
> I picked up my 86 325e about 3 weeks ago.

Congratulations on your new toy!

> Yesterday while cleaning the engine I noticed that a black 
> lead on the right side of the engine had been unplugged. 

Right under the empty battery tray near the firewall on the passenger side?

> Thinking that I had knocked it out while cleaning, I plugged
> it back in. After that when I drove the car it was idling 
> really badly and would cut out for a few seconds whenever I 
> put my foot down. After I unplugged the connector the engine 
> seemed to run fine. Its two black plugs that come together 
> with 2 male and one female pin inside. 

If I guess the location correctly, it's your oxygen sensor harness.
If the sensor is bad, disconnecting it will improve derivability.
When unplugged, the DME goes to default (open loop) operation and quits
optimizing the fuel mixture. The engine will run smoothly, but if running
too rich will clog your cat before too much longer ($$$). You want to buy a
replacement 02 sensor and reconnect the harness!

> It turns into a pair of wires that disappear somewhere down 
> below the engine.

It goes to the 02 sensor screwed into the headers. Follow the wires from
under the car and you will find it. If it's the original, 14 years of road
grime will complicate the removal of the old sensor. You may have to take it
to a mechanic to do the job anyway if you've never worked on your cars in
the past.

good luck,
alex f

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