?s re VAG-COM Readings

benswann at comcast.net benswann at comcast.net
Sat Sep 20 03:08:55 EDT 2003


My understanding of the readings and interpretation with respect to the manual
is the engine is running rich.  Your IME describes what I believe is happening.

Anyway, I did change out the O2 sensor just before getting swamped by Isabel,
so will be a few days before I can tell if this did any good.  I would think
this would help rule out the O2 sensor, yes?  If I don't see an improvement in
fuel economy and throttle response, and readings are still off, then perhaps
fuel pressure and other tests are in order.

I am sure the engine is not running lean - plenty of power and plugs looked

Thanks for the tips.

> First fuel injector test:
> pull the electrical connector off each fuel injector.  When you get to the
> one that doesn't change the running motor sound, that's the cylinder with the
> problem (spark OR fuel).  Then, you can swap it for another one in the bank, to
> see if the suspect cylinder comes back.  If you already have the O2 sensor,
> swap it in and see if it works.  IME with 02, the first indication in the
> failure is a massive drop in the fuel mileage.  They also tend to become slow to
> react.  If you hook up a no load voltmeter to the 02 and read the voltage while
> blipping the throttle.  Or if you can get a reading from VAG com or other test
> equip, you should see lambda approach .9 as you blip the throttle, then return
> to 1.0 +/- within a few seconds of releasing the throttle.  IME 2 O2 sensors
> bad tend to run on the rich side, not the lean side of stoich, and lean is
> what you have IMS.  When I see lean O2 readings, I think either air leak or bad
> injector.
> I'd also caution again that sometimes 02 sensor codes are because something
> else is causing them to happen.  New O2 might solve the problem, my concern
> would be that it's just covering up the problem.  In which case, in my case, it
> would be back in my shop, in your case, we might well revisit this thread.
> Scott J

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