Unofficialbmw.com

free4unet.com · Joined: 23 Jun 2003 Posts: 2 Location: Virginia

Hi,

Before I go out and spend $$$ on having my engine checked, does anyone know what the check engine warning can be caused by ? Monitoring the engine performance, especially when accellerating, it might be a problem with the oxygen sensor(s). If that is the case, do I have to replace both of them at the same time and where exactly are they located ? Do I need a mechanic for that or can I do that myself (having quiet some handyman skills) ?

Thanks for any feedback,

Andreas
akraemerus@yahoo.com

mwong · Joined: 23 Jan 2000 Posts: 69 Location: Seattle, WA

Your gas cap is on tight and still has a good seal, right?

I believe that in the 2000's there are four O2 sensors, two pre cat and two post cat.

In 1995, I think there are only two. Unplug, unscrew, replace. No special tools required. Open ended wrench (can't use a socket due to wires) and flatblade screw driver to open electrical connector cover.

Check places like bavauto.com or Crevier BMW for best prices. $120 each?

BMW recommends O2 sensors be replaced every 100k miles. A sign that yours are failing is reduced fuel economy and poor idle.

Good luck!

rbunch4468 · Joined: 01 Nov 2002 Posts: 11 Location: massachusetts

Before you purchase replacement O2 sensors, it might be worthwhile to do a simple inspection of the vacuum lines leading into the rear of the manifold. I experienced a similar 'check engine' report, along with a rough idle which was caused by a split vacuum line. If you remove the top engine cover, you can listen for a localized 'sucking' sound, as these engines pull a strong vacuum. Once you have a general idea if there is a leak, you may further track it by feeling around the rear of the manifold for air movement. Your diagnostics will be lead as much by sound changes in the air flow as by feel.

In my case, a replacement vacuum line remedied the problem.

Good luck!

Rick

free4unet.com · Joined: 23 Jun 2003 Posts: 2 Location: Virginia

Hello Rick:

Thank you for your reply. I noticed that the technican who was working on my car last (a few months ago) did not fix two of the four screws for that cover. The two on the left - standing in front of the car looking at the engine are missing. Do you think that this might cause problems too since the cover is not pressed down on the engine block ?

Any idea where I might get replacement bolts/screws ?

What costs did you experience for the vaccum line ?

Thanks for your great input,

Andreas

rbunch4468 · Joined: 01 Nov 2002 Posts: 11 Location: massachusetts

There is the plastic engine cover held on by four 10mm nuts...This is just cosmetic... and there is the cover at the rear of the intake manifold, which is the connection for the crankcase ventilation.

This is the one that you ought to inspect carefully. If the technician left out fasteners from this cover, this may be a source of vacuum leaks. Vacuum leaks = bad.

In my case, the one port that was leaking badly had a torn cap. I replaced the cap with a generic one purchased at my local auto parts supply. Whether or not this port was capped from the factory, or added later is an investigation for another day.

Rick