OXS CQ, Interval

["Keleigh Hardie" <hobbesian@worldnet.att.net>]

Duane says:

> This brings up a perennial question.
> 
> We all know the interval is useless, but how do you tell when the
> O2 sensor is going/gone? Is there a seat-of-the-pants method, or is
> the official test procedure required?
> 
The best way is with a ammeter. Excessively large fluctuations in the
differential pressure current, or none at all. An emissions tester can be
helpful as well.
>
> The reason I ask is that my '89 100Q has 140K on the original
> sensor, and has been exhibiting some symptoms for a while now.
> 
> Gas mileage is not as high as it could be (but my lead foot might
> have something to do with that).
>
Or the high mileage, though on a well maintained 5cyl that shouldn't
matter. I assume you've already checked the obvious, the right plugs etc.
>
> Full throttle kind of "bounces" or stumbles a bit (doesn't full
> throttle ignore the sensor?).
>
Full throttle should be open-loop, though may not be if the full throttle
switch isn't working. A surge a part throttle or idle would be more likely
to indicate a bad OXS, V8's are notorious for this. For full throttle,
check again ignition, or fuel flow.
>
> Not-quite-cold throttle response is terrible (???)
>
You might want to check the air flow sensor potentiometer on this one.
Also, the coolant temp sensor (I believe its a black two-prong on this one.

Finally, if you've got the manual (and you really should), run the fault
codes. It only costs borrowing a spare fuse, and would probably pick up a
lot of these problems.

88/80Q (soon!)

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