Failed Emission Test

[edwulf]

Ok, Guys and Gals,

I need some quick input.  As is typical, for me, I've put off emmissions testing until the last second.  Now, the '89 100 2.3 auto non quattro has failed.  Here's the info:

Hydrocarbons Loaded Test: Pass
    standard = 220ppm  -  my reading = 91ppm
Carbon Monoxide Loaded Test:  Pass
    standard = 1.2% - my reading = .33%
Hydrocarbons Idle Test: Fail
    standard = 220ppm  -  my reading = 379ppm
Carbon Monoxide Idle Test: Pass
    standard = 1.2% - my reading = .04%

Car has new Bosch plugs, cleaned throttle body last week, has been driving well, self diagnostic = 4444 (good).  Air Cleaner less than 6 months old.  But, the idle has been a bit rough over the past month.  I'm thinking - Idle Stabilizer Valve.  Wouldn't that set a trouble code?  My other thought, iffy O2 sensor.  Wouldn't that, also, set a trouble code?  Since I've had it, I have not replaced the plug wires, cap, rotor, nor have I done the timing belt, if that makes any difference.

Any Thoughts?

Thanks,

Eric Wulf
'89 100
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