Getting an old Audi to pass emissions inspection

My trusty 89 Audi 100 failed the Texas annual emissions inspection, with excessive HC at idle ( 373 vs. the 220 limit ). All other parameters were
under the limit, including HC at speed. The inspection station said to get an additive from O'Reilly Auto Parts called "Guaranteed To Pass", and run it through a tank full of premium gas with Techron. Then run the car for about 15 miles to get it good and warm before inspecting it again.
I have 15 days to get the car re-inspected without having to pay another $40 fee.
What do you think of their advice? Do you have any other suggestions?
FYI, the car has been maintained by the book by a very competent Audi mechanic, and it is current on oil changes and tune-ups; all the basics are correct. I also add Techron at every oil change. He says it may need a new catalytic converter. The odometer stopped working several years ago, but I estimate the mileage at around 300K miles. I only put about 4000 miles a year on the car now, so it is driven mostly in town two or three times a week for short trips.
Thanks for your opinions!
--
Stephen Clark
89 Audi 100
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Stephen Clark wrote:

The four T44s that I used to have never had a problem with inspections.
Try to replace you air filter.
Your mechanic probably is familiar with the ISV Idle stabilization valve and the throttle body switch that activates its controller. You might want to have its function checked.
If yours has an O2 sensor, that might need replacing.
There is also an adjustment for injector frequency (I don't remember what it is called) that can adjust rich / lean conditions. Your mechanic could look at adjusting that with a dwell meter.
The first thing I would do is to try the suggestion of the inspectors with the "Guaranteed To Pass" and the Techron. It might just be dirty injectors.
Let us know how it tests.
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distributor too far advanced bad spark, spark plug or injector air/vacuum leak maybe at injector seals debris on intake valves soaking up fuel before it enters the cylinders mixture too lean (CO adjustment in fuel distributor)
engine problems? TonyJ mentioned the throttle switches which might have broken wires. I think your fuel injection has the electronic fuel pressure regulator which can be adjusted with a Digitasl Volt Ohm Meter.
So new air & fuel filters, spark plugs & wires, oil change would be the second thing to do after a compression test. ;-) but these things have been done! ;-)
--
later,
dave
(One out of many daves)
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Thank you all for your suggestions. After running the gas treatment through a full tank of premium, the HC at idle was reduced by about 100 points to 285. The limit is 220, however. My mechanic says to run another can through and see if it will get it under the limit. Is this a good idea? Are the effects of the intake system cleaner cumulative?
--
Stephen Clark
89 Audi 100
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It sounds like you are on the right path. Can the distributor timing be retarded a little on your engine? Can you give it a nice long run on the highway with the cleaner in it?

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I did just exactly that on the first go-round. Ran it on a weekend trip, and even performed the old "Italian tune-up" - running it in second gear at about 5000 RPM for a few brief bursts.
I don't know about retarding the timing - isn't it controlled by the computer via knock sensors?
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Stephen Clark
89 Audi 100
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Stephen Clark wrote:

It is limited by the knock sensors but I thing you have some control in adjustment with the distributor. If the distributor adjustment bolt is still covered by the factory tamper shield you would need to use a hand grinder to take that off before adjusting. Mark the distributor location before changing it.
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So on your '89 your ign spark is timed using an Engine Speed Sensor and not the distributor? The only 100 I have seen needed a new Crank Sprocket.

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I know it has knock sensors, but I don't know about an engine speed sensor. Seems like there is a Hall effect sensor, but I don't know if that is involved in timing or not.
I didn't think that the timing was adjustable at the distributor, but according to Tony J it is adjustable at the distributor, if you defeat the tamper shield. Haven't looked at it yet to see, though.
Stephen Clark 89 Audi 100 Houston, Texas USA

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