Failed Smog Test - California

[BlackOnBlack]

'92 525iM, 174,000 miles.
I've had it 2 years. Got it with 142000. Runs great. No Engine codes. 22 mpg mixed consistent since I got it.
Took it in for smog today.
Failed miserably at low and high speed...Gross Polluter.
NOx limit is ~ 750...mine was ~ 2000 both speeds.
HC limit ~ 100...mine was ~ 250 at both speeds.

Catalytic Converters?
Oxygen Sensors?
General Tuneup?

I'm dreading the cost of getting it figured out.

Any advice?
Thanks,
Steve

[colo525i]

First thing.. did you go run the car on the highway and have it tested promptly after doing so? If not do that, you can fail if the cats are not hot enough. If you did make a highway run, I'd go ahead and replace the air filter, spark plugs and 02 sensor.

[BillionPa]

exactly what colo said.

if you still fail after that, the cats are probably dead.

the fact that it got both nox and hc high leads me to believe it wasnt hot enough.

[BlackOnBlack]

thanks, guys. I'll try all the little stuff and then get it nice and hot. I left work for lunch and just decided to get it done. It was opeating temperature by the time I got to the shop but had only run @ 10 minutes...and a cold day.
I just noticed something though...15 mph was done at 1769 rpm, 25 mph was ddone at 1875 rpm. Not much difference in engine speed. I also noticed that when he upshifted on the dyno, he lugged it a bit and it pinged somewhat. Wonder if that could have caused high readings? Could the fact that I run 235/45-17's all around make any difference? I bought it with those on it two years ago.

[BillionPa]

if its an automatic, those rpm readings are perfectly normal. i can get all the way to 85mph without passing 2500rpms.

on a manual though, i could see if the test would have simulated increased load in the next gear at a similar engine speed.

the same conditions inside the combustion chamber that would cause pinging can and will cause lower operating efficiency of the engine and significantly higher readings on the test.

suggest BG44K + Techron + 2 cycle oil in the tank with premium gas to remove carbon deposits over the next 150 miles before taking the test again, as well as getting any potentially helpful tuneps done, like spark plugs, fuel/air filters, thinner low SAPS oil, and put a bit more air in the tires so they have lower rolling friction on the dyno.