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Discussion Starter #1
It's time again for my annual emissions test (aka: wasting 1.5 hours waiting to be oppressed by the local government that blatantly reminds me daily that they have no intention of representing me). I usually take my S3 Veloce to my trusted Alfa mechanic for the tweaks needed to get through the emissions test, but this year I would like to skip the trip to the mechanic.

I just searched the archives for 40 minutes, but couldn't find the answer to my question. Can someone please tell me which way (clockwise or counter-clockwise) I should adjust the idle mixture screw on the AFM to lean out the mixture?

Thanks, Cory
 

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How do you know it needs to be leaned out? A lean mixture will not always help a car pass emisions testing*.

With a functioning O2 sensor and catalytic converter your Spider shouldn't have any problems passing an emisions test. Make sure it is fully warmed up - the single wire O2 sensors depend solely on exhaust gasses to warm up the sensor (the later models have a built in heater to get the sensor up to temp sooner). Also, an oil change is supposed to ge a good idea.

You can use the car's O2 sensor to adjust the idle by-pass screw. Click on the link in my signature block for the L-jetronic diagnosis page. See step #11.

*So, long story: Our '78 MGB is supposed to have a single Z-S carb and catalytic converter plus air pump. I 'de-smogged it' and converted it to dual SU's. My local garage said they'd pass me if I could get it to pass the tailpipe 'sniffer'. After breaking in the rebuilt engine we hooked it up to their exhaust gas analyzer. I had tuned it up then adjusted the carbs to the lean side. It was close to passing but one of the measured chemicals (CO or HC's) was a wee bit over the allowed limit. As I adjusted it a little bit leaner, it got worse! I re-adjusted (i.e. towards rich) back to 'normal' and the measurements improved. So, lean may not be the answer. A correct mixture is best.
 

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Discussion Starter #4
To answer gnhl's question:

Both of the mechanics I've used since I've had the car (Stephens Alfa in FL and Tim Tilley in Memphis) have recommended that I run the car with the o2 sensor disconnected.

When I moved back to Memphis and had to get the car inspected last year for the first time in 4 years, I put on a new cat, new o2 sensor, new plugs, and a new K&N filter. The car still failed the test miserably, so I took it to Tim and watched what he did.

Disconnect o2 sensor
Lean out the idle mixture, but no so much that it stumbles
Lower the idle rpm to around 600

Result - passed test.

I know that a properly tuned and functioning L-jetronic system will supposedly pass an emissions test, but mine never has in Memphis. I don't trust the test equipment or operators (it's the gub-ment - duh) and my car runs great otherwise, so I don't plan to spend the time and money to figure out if something's wrong with the L-jetronic.

Thanks for everyone's help.

Cory
 
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