IML: '82 coupe rough idle

[Nat Hall <nathall@xxxxxxxx>]

Hey list,

Some of you may remember I recently had my '82 fail the smog test because
of CO emissions that were too high during the treadmill test (CO at idle
was OK). Well, I decided to start simple and I replaced the O^2 sensor
since the old one was obviously toast.

That had an effect, but I'm not sure what it means.  Now the car seems to
run better overall while in motion and *seems* to have better power while
accelerating.  But now the idling has gone to crap. All I did was change
the sensor, nothing else.  The idle is rougher than it used to be,
especially when started cold-- it even stalled once on me the other day
when I was trying to warm it up. Once it's warm, the idle is still rougher
than it used to be but not so bad it stalls.  Regular driving it runs
great, like I said, maybe better than before. Absolutely no problems or
even hints of problems at all. What gives?

I know enough about engines and cars in general that I can easily get by
working on them as long as I have a FSM, but diagnosing obscure
carburetor/vaccum/emission related stuff is my weakness. Now that I have a
known-good O^2 sensor, do I just need to adjust the idle speed on the
carburetor? I didn't think I should have to do that. Anything I should look
into before that?

Also, not sure if this is related, but I found I have an exhaust leak
somewhere on the passenger side in engine compartment. My guess is the
passenger side manifold, but I can't find out exactly where it's coming
from. Could this be allowing excess oxygen in during idle and screwing up
the sensor's signal causing the roughness? If so, then why wouldn't this
affect the way the car runs while driving? How hard is this going to be to
track down and fix?


-------------------
Nat Hall
1982 Imperial Coupe
-------------------




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