Miatapower List Archive

This read-only message was archived from a public mail list.
Mail From: "Victor Harder" <(email redacted)>

Some wierd readings have been showing up on my '90 1.6L Autorotor, 8PSI,
with J&S. While driving well after warm up, the A/F guage will go full
lean, long enough for the check engine light to come on. Then it will
behave as if it is warming up, slowly creaping towards 14.7 and then
going back into normal zero-crossing behaviour again. Happenned twice
on a 150mile trip, both times when the engine was good and warm (not hot
or overheating).

It happenned in traffic on the way to work again too. The engine seems
to run fine during these events.

This is a stock single wire O2 sensor.

Ideas? Is this something to be concerned about?

vic

This read-only message was archived from a public mail list.
Mail From: "Victor Harder" <(email redacted)>

Yes, that is when it has happened so far... but then it comes back to
life without changing the engine load too.

Question: if this is happening, is the ECU really running the engine
lean? I checked the plugs, and they seem OK... so i'm not sure who is
lying, the O2 sensor or the ECU.

vic

Ray Ayala wrote:
>
> Victor Harder wrote:
> >
> > Some wierd readings have been showing up on my '90 1.6L Autorotor, 8PSI,
> > with J&S. While driving well after warm up, the A/F guage will go full
> > lean, long enough for the check engine light to come on. Then it will
> > behave as if it is warming up, slowly creaping towards 14.7 and then
> > going back into normal zero-crossing behaviour again. Happenned twice
> > on a 150mile trip, both times when the engine was good and warm (not hot
> > or overheating).
> >
> > It happenned in traffic on the way to work again too. The engine seems
> > to run fine during these events.
> >
> > This is a stock single wire O2 sensor.
> >
> > Ideas? Is this something to be concerned about?
> >
> > vic
>
> If this happens only during moderate-to-low engine load (and thus lower
> exhaust temp) it may be a sign of a dying O2 sensor. When they're
> nearing end-of-life they have to be kept hotter than normal to
> function. We usually see this kind of symptom during idle at first.
> Keep us posted. - Ray