My 1996 M3 failed emissions today

[tyco1983]

HELP: my 1996 M3 failed emissions today

Hey guys,
I failed emissions today with the Bimmer. Its a 96 M3 with a Shark reprogram, intake, and tri-flow exhaust. The check engine light is NOT on, but it failed emissions today as a gross polluter because of the extremely high NOX levels. Would this mean a bad cat? What else could it be? I'd like to narrow it down before i take it to get fixed so I can maybe save a little dough. Any and all help appreciated.Taylor

ps-what kind of negative effects is this having on the peformance and gas mileage? [???1] [???1] [???1]

 

[Kirby]

Did you reset the Shark settings to factory original spec before inspection? I'm thinking that since the Shark tunes the ECU for performance, it might have increased emissions? I know that peak performance and low emissions are usually mutually exclusive.

 

[knightpitt]

NO2 is a sign of unburnt gas. Typically, high levels of NO2 are a sign of needing new O2 sensors. It is also possible that the Shark Injector lets the A/F run a bit rich in order to keep advancing the ignition timing safe. However, I bet that your culprit is the O2 sensors. If that is the case, you'd likely notice a drop in gas milage recently (or since the last passed emissions). Also, if the Shark was causing cars to run so rich that they'd fail emissions on NO2, they wouldn't sell them. They'd reduce gas milage so much that no one would purchase them.

So, the best guess: get a new set of O2 sensors (I think you have 4).

 

[Kirby]

Wouldn't a bad O2 sensor cause the check engine light to be on and throw a code?

Also, from what I understand NOx is the result of lower fuel concentration. When tuning an engine, you generally lean out the fuel as much as possible to optimize the ratio and get the most power, but causing higher emissions.

"Smog is formed due to improperly burned fuels. In cases where to much fuel is presented to the engine cambers high levels of Carbon Monoxides (CO) are emitted through the engine tail pipe. In cases where low fuel levels are presented, once again the fuel burns improperly and now the engine produces low levels of CO, but begins to emit high levels of Nitrous Oxides (NOx). The engine may also miss-fire due to inadequate fuel, creating excessive Hydrocarbons (HC).

The optimum performance level is achieved when the engine can maintain a 14.7:1 air/fuel ratio during the combustion process with a constant variation +/- 5% to assist the catalytic converter operation. "

 

[tyco1983]

Well I definately have noticed a gas mileage drop since last emissions testing. I'm getting about 20mpg (200 miles on 10 gallons) when driving nice and I used to get around 23-25. But now i'm a little confused because both of your posts make sense.

 

[Kirby]

Part of what the cat converter does is to reduce NOx. I suppose the cat could be bad also. Best bet is to have a shop put it on an analyzer and see what comes up. But at least you are armed with a few ideas about the causes of high NOx.

 

[gpoints]

Hey guys,
I failed emissions today with the Bimmer. Its a 96 M3 with a Shark reprogram, intake, and tri-flow exhaust. The check engine light is NOT on, but it failed emissions today as a gross polluter because of the extremely high NOX levels. Would this mean a bad cat? What else could it be? I'd like to narrow it down before i take it to get fixed so I can maybe save a little dough. Any and all help appreciated.Taylor

ps-what kind of negative effects is this having on the peformance and gas mileage? [???1] [???1] [???1]

Being a gross poluter sucks big time. Unless the laws have changed, you have to go to special smog shop to pass this time AND the next time you go. 1st I'd reset your PCM back to its factory settings. If the Shark is advancing your timing, it could be contributing to the elevated NOX. Also, are you experiencing any type of PINGING? Check for a vacume leak and make sure all of your vacume lines are connected correctly. Good luck.

 

[tyco1983]

i'm assuming the knock sensor would prevent any pinging so no, i don't believe it is. Dave from turner motorsports says all their cars now have to pass CA emissions, and none of the shark programmed vehicles have had any problems.-Taylor

 

[gpoints]

i'm assuming the knock sensor would prevent any pinging so no, i don't believe it is.

That is not an correct assumtion. All the sensor does is retard timing once in sees knock. If the computer is retarding your timing there is something wrong. Could be gas, could be carbon in the combustion chamber, could be a lean condition...

edit: I just noticed you have an intake on your ride. Is it on there good and are all your sensors connected? More than once I've removed things and just forgot to plug them in.