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Old 04-11-2005, 11:21 PM
Duke2.6 Duke2.6 is offline
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Join Date: Mar 2003
Location: Southern California
Posts: 2,270
Well your test results do not quite fit into the "norm".

Usually the HC problem is at 15 MPH when the catalyst is cool, but the 15 MPH test heats it up so the 25 MPH numbers are lower. It looks like your test two years ago was a two-speed no load test, so you must live in the Bay area where the ASM test was just implemented last year. Even though the previous test was no load, there appears to have been an increase in emissions. What was the odometer reading for the two tests? This could be a case of catalyst aging, but it's not that bad!

You have a bit of O2, which means that if the catalyst were hotter there would probably be more oxidation reaction, so If you know how to alter the ignition advance curve for your engine, that will probably do the trick.

I know how to do it for M103 engines, but I'm not familiar at that level of detail with the '94 fuel and igntion systems, so I can't give you any specific "how to" advice for your model.

The CO tells me that the mixture is within the stoichiometric sballpark, so I don't see an O2 sensor problem, but I would want to look at its wave form on a scope to determine if its response time has degraded. Most shops will just want to replace the O2 sensor, and that may help or not. See the nearby thread where someone had the catalyst replaced and the emissions INCREASED.

There is no substitute for good analysis and testing beginning with understanding what the data on the test report is telling you. You would think that these mechanics were never taught this information. They were, but you would never know it. Most of them seem to have forgotten everything they learned when they got back to the shop and back into the old routine of swapping parts for an hourly rate until they end up fixing the problem, if they ever do before the customer walks off in a huff and trys someplace else.

There ARE good emission repair techs out there, but they are damned hard to find!

Get back to me with the mileage on this and the last test, and also let me know if you the O2 sensor (s) has ever been replaced.

BTW if you were directed to a "test only" station, you can get cost recovery of repairs regardless of your income (don't need to be "low income" to qualify).

Details at


PS I'd also like to know the "test weight" for your car and the software version number. Both are on page 1 of the test report. The test weight should be near the top of the report and should be about 300 pounds more than curb weight. The software version number is in the information field just above the signature block. My test on 3/03/05 was version number 0403/ES974825.

Last edited by Duke2.6; 04-11-2005 at 11:34 PM.
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