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Failed Texas Emissions Testing


My 1994 BMW with 163,000 miles failed the emissions portion of the state inspection twice. Below are the results of the second test, which was performed AFTER a mechanic replaced all spark plugs, did a fuel rail injector service(?), replaced the mass airflow sensor boot, and replaced a vacuum hose.

High Speed Results

HC (PPM) 120/170

CO(%) 0.67/1.72

NOx (PPM) 848/66

Low Speed Results

HC (PPM) 124/205

CO(%) 0.69/1.74

NOx (PPM) 937/165

I was given the following report after testing: Transmission shifting okay, no misfire, no smoke, fuel control okay, O2 sensor okay, not overheating, no air injection system, cat not responding – and told to take it to another shop to have the catalytic convertors replaced.

The second shop absolutely does not want to replace the catalytic convertors, telling me that is absolutely NOT what is wrong with this car because the NOx results are so low. That it simply cannot be the case.

Now what? I’ve failed the test twice, as I said. There’s no guarantee that new catalytic convertors will fix the problem and one shop is saying that it absolutely is NOT the problem. What to try next. I love this car and want to keep it.

Did the test results also show the percent O2 and the percent CO2 values? If there is excess O2 in the exhaust gases, I would suspect the catalytic converter. If there is very low O2 precent in the gases and the CO2 percent is close to stociometeric, I would look for an uncommanded rich condition i.e. leaking injector, leaking fuel pressure regulator, etc.

Hope this helps.

High Speed = 13.9
Low Speed = 13.9

High Speed = 0
Low Speed = 0

Seems like there is no O2 present, eliminating the catalytic convertors.

Where do they test emissions in Texas? When I am in the States, I live in McAllen, and they do not check emissions. I wanted to find someone to check mine in case the laws in Mexico change, and I need to pass emissions there. I asked and no one had the equipment to check emissions. It was suggested I go to Corpus or Houston, which is a long drive for something optional at this point.

What city do you live in?

I bet if you install new converter(s) it will pass the test with flying colors…Aftermarket converters will do, no need for pricey factory parts…With no air injection, your car will need “3-way” converters to work properly…


I live in Dallas also. I had a 1983 Landcruiser that could not pass emissions test, even after spending over $1,200 in repairs. I finally spoke with someone either at the DPS Field Station in Plano, or with AirTechTexas. They said they have a location where vehicles that have repetitively failed inspection can be brought and this location has a 95% success rate.

It is a state facility, not privately owned. I spoke with the guy in charge, and he said they were finishing up a Ferarri that no one else could get to pass emmissions. I will try to find the number for the facility. It’s been a couple of years.

I just remembered, I think I was living in Colorado when this occurred, and I spoke with someone at a state facility in Denver. Nevertheless, it would be a good idea for Texas DPS to have a facility to analyze vehicles which have failed inspection multiple times. Say, if you have failed 3 times, you would be eligible to go to this facility and get their expert evaluation of the cause of failure. It would certainly fix a lot of high emitting vehicles.

My '90 SAAB failed an emission test once: Bad o-ring on the gas cap if you can believe it. Never had a problem with the catalytic converter in all those years though.

It is amazing, though, how many clunkers have returned to the road since they stopped testing here in oHIo.