Took my car to inspection today.

1993 del Sol w/ OBDII B18C1 running a chipped P28
i/e as far as mods go.

Failed emissions.

NOx - limit = 1372 | scored myself a 179 PASSED
HC (Hydrocarbons?) - limit 173 | scored myself a 211 FAILED
Carbon Monoxide - limit = 0.97 | scored myself a 5.21 FAILED

Anyone know what would cause these readings? My CO was unbelievably high and my NOx was extremely low. Some of the possible reasons I was told were O2 sensor and running rich from the chipped P28. No one really knew about emissions though, it was just guesses. I'd appreciate if anyone could explain to me what could possibly cause these readings so that I can either fix it myself, or take it somewhere with a heads up as to what needs to be done. Thanks in advance.

If I missed giving any important information, let me know.

 

Come on guys, help a brotha out.

 

First thing I would say is lose the Chip, at least for the test.

For the test, I would:

1) Run the lowest octain gas the engine will tolerate without knocking.
2) Run your timing to the high end. (18 if the spec is 16 +/-2)
3) Make sure the cat is fully hot for the test.
4) Add 2 bottles of HEET gas line drier to a half tank of gas.

DO NOT take the test with any injector cleaner or other cleaning additives in the tank. If you used any recently, run 2-3 tanks of clean fuel through before re-testing.

These are the things I did after I failed the IL test and the re-test went fine.

 

The real problem lies in the CO. Fixing the CO should allow the HC to follow up with better numbers. Even with a limit of .97, a 5.94 is way off the chart. Most cars with passing CO will score numbers like <.3. But I think the advice you were given to lose the chip and check the 02 were correct. It's something in the computer control of the mixture unless you're pouring out smoke from a severely worn engine, which I can't imagine. Do you have any codes stored? Check that, and also try to use a stock ecu. I can't see changing what's in the fuel tank getting the C0 from almost 6.00 down to .3. The NOx being so low could be normal, but should be 300-600 on average. So it's probably running lean. Replace/clean your air filter also.

 

got a p72 ecu?
i think putting that on and putting it back to stock would clear everything.

 

Thanks for all the help guys. I don't have a P72, but I can get my hands on a loaner ECU. I'm also looking into possibly replacing the cat. It is the original cat with 138k on it.