trouble passing State of Texas emmissions

[texasporschedude]

I am having problems getting the car to pass the Texas state emissions test. It is failing on the low speed HC standard is 148, it has scored 349 and 541. The high speed passed at 143. I have replaced the fuel injectors, distributer cap rotor and plugs.

The crazy thing is we ran a test and it passed, then ran the the emiisions test imeediatley following and then it failed. Ideas on what to change?

The cats are about 7 years old with less than 25K miles. Not sure if the O2 sensor can cause this, based on the test, it is running lean.

[Rich Euro M5]

Don't change anything until you run some diagnostics. Have you looked at the output of the O2 sensor to get an idea what's going on with the A/F ratio. It's very important for the A/F ratio to swing lean and rich through stoichiometric, this is what makes the catalytic convertors do their job.

You mentioned the convertor was changed out about seven years ago. Was a new OE convertor assembly installed or where some sort of aftermarket convertors welded in? If you have aftermarket convertors consider them suspect.

Rich

[texasporschedude]

Thanks Rich.

I dont have the pin assignments at the diagnotic port so I will need to test the O2 at the sensor plug. I am working from the Bentley 535 manual as I cant find a M5 manual. The car is running like a beast after I added new injectors and plugs,

[mooseheadm5]

Definitely check the O2 sensor. If it checks out you can lean the idle mix via the mixture screw on the AFM.

[texasporschedude]

Ok, I checked the O2 sensor. It range from .2 vdc to .650 at idle and increased to .85 at higher RPM. I took the oil filler cap off and it dropped to .150. I am not sure of the volatage ranges but it appears to be working. Any tricks to know on adjusting the air mixture?

[TurboChris]

Being 7 years old or 25,000 miles, doesn't really tell you anything about the condition of a converter. But a new QUALITY converter (made in USA NOT China) will do a LOT towards cleaning up a dirty motor. Case in point....My M5 couldn't pass last week till we put a new converter on it. I'll bet that's what it's gonna take.

[texasporschedude]

It may fix it. Seems though something else is wrong for the fact it is running rich, which is why it is failing the test. Can anyone recomend a good BMW mechanic in Dallas who knows these cars? BTW what brand cat did you buy?

[Rich Euro M5]

Ok, I checked the O2 sensor. It range from .2 vdc to .650 at idle and increased to .85 at higher RPM. I took the oil filler cap off and it dropped to .150. I am not sure of the volatage ranges but it appears to be working. Any tricks to know on adjusting the air mixture?

If the O2 sensor voltage is swinging between .2vdc to .65vdc at idle the A/F ratio is correct at idle. Stoichiometric A/F ratio occurs at about .5vdc.

Most likely your catalytic convertor has died, particularly if it's an aftermarket convertor.

Rich