'91 80q emissions

[Jonas K.]

On 6/19/02 12:11 PM, "Brandon Rogers" <brogers at terrix.com> wrote:
>
> My sister has a '91 80q that has had some serious work done by the dealer
> recently because it failed emissions a few months ago.
>  HC was .5 where the limit is 2.5--Ok in that category.  But CO was 22 where
> the limit is 20.  Any ideas?  02 sensor?

When was the O2 sensor last changed? If more than 60k miles ago, then I
would suspect it. But I wouldn't replace it automatically, test it.

Typically high HC or CO emissions are a sign of running rich. Even without a
catalytic converter, the car is clean enough to pass (if well tuned up).
There could be any number of things that cause a rich condition.

O2 sensor
Faulty ECU/wiring
Cold start enrichment always on
Fuel pressure incorrect
Malfunctioning fuel distributor/DPR
Leaky injectors

What exactly did the dealer do, and why did they do them? There are pretty
specific tests to figure out which component is malfunctioning, so there
should be no need to hapazardly repair emission control devices.

About the change in idle, etc. Sometimes a problem is masked by an
adjustment unrelated to the problem cause, so that when the actual problem
is fixed, the unrelated adjustment causes a problem by itself. For example,
a slight air leak after the air-flow-sensor will cause rough running, this
can sometimes be masked by adjusting the CO-adjustment screw. Years later
the air leak is fixed, but now it runs like crap because the fuel mixture is
off at idle. Food for thought.

A tune up is always good to do also. Plugs, cap, rotor, oil change, fuel
filter. Make sure the plug wires are still good. A spark miss will result in
high HC's, but it never hurts to check.

HTH,
Jonas