'94 530im Fails Emissions Test

[Super90]

OK, the old 5er just failed the Texas State Emissions Test. Car has 140k mi. on it, and has been very carefully maintained according to prescribed schedules. No codes thrown in a while and the most recent one was for an O2 sensor, so I put in two new ones from BMA about a year ago.

Here is the data from the test:

HC (PPM) 228 max allowed 112 FAIL
CO (%) 0.49 max allowed 0.62 PASS
CO2 (%) 14.5
O2 (%) 0.6
Nox (ppm) 1156 max allowed 829 FAIL
Dilution 14.99 need >6 PASS



Question is, what to do next? Seems like I am way out of range on Hydrocarbons, so is trying another testing facility worth the $40 ? Is there any way to do some troubleshooting on my own ? Car doesn't have OBDII, so there were no other data available. Or, do I just need to go to the local indy and have them diagnose ?

TIA

[yaofeng]

Bad cats will cause the HC to be out of wack, sometimes NOx also. Are the cats original? If it turns to be the cats it could be expensive.

[Super90]

Yes, I am afraid it could be the cats, and yes they are very expensive. Last time I priced them they were about $1200 ea, IIRC. That is the very, very last thing I would be willing to replace. All other rocks will turned over first.

I just put some Redline Fuel System Cleaner in the car just now and will run it hard for a few days. It doesn't get a good workout in my normal commute to the office and back, so maybe there is some carbon build up going on. Also, if I understand the M60 motor, there is no EGR system, and the car relies on the cats to do a good bit of the work. I have a feeling the car sat too long before the test was performed and they were not really at proper temp. so getting them good and hot before the test could help a bit. I always run premium gas in it but we are in an area with up to 10% ethanol. Would that help or hurt?

Ideas ?

Thanks again.

[AngryPopTart]

Is that $1200 for factory replacements? On my 525i I just use an aftermarket replacement and it passed just fine, and it was alot cheaper than the factory replacement cat.

[Super90]

Yep, they were OE cats from BMA, but that was about four years ago when I priced them. Aftermarket cats for M60 cars were a bit dodgy back then and no one really recommended them.

[Lordsneldon]

Yep, they were OE cats from BMA, but that was about four years ago when I priced them. Aftermarket cats for M60 cars were a bit dodgy back then and no one really recommended them.

I wouldnt bother going to the stupid expense of changing the cats when it is most likelly the lambda sensor which sits in the cats. Give that a go first it'll probably cost you less than £100 ($198)

[Super90]

Aren't lambda sensors the same as oxygen sensors (aka "O2 sensors") ?

If so, that was done about 6k miles ago.

Many thanks,

R.

[bubba966]

Aren't lambda sensors the same as oxygen sensors (aka "O2 sensors") ?

If so, that was done about 6k miles ago.

Many thanks,

R.

Yes, they're the same thing.

[Paul in NZ]

and it will make some difference is oil is fresh,car(and cats) are hot....run some injector cleaner through too,just before you change the oil.

[Super90]

We'll do. Thanks !