HELP! Failed CA smog with High NOx and HC numbers

[Freude am Fahren]

Hi Folks,

My first post here. I own a all stock 1991 318i with 113K miles on it and yesterday I failed smog with high HC and NOx numbers in the 15mph category. Everything else, i.e. CO, was within the acceptable range for the 15mph. In the the 25mph, all the numbers were low and acceptable. What could be wrong? Here is a history of what I have replaced:

- Cat was replaced Summer last year (107Kmiles then)
- Spark plugs replaced Summer last year
- Mess under the intake done Summer last year
- temperature sensors replaced Summer last year
- CPS replaced last year
- Fuel pump and FPR replaced last year
- Air filter and fuel filter replaced last year
-ICV cleaned Summer last year

Here is what wasn't replaced:
- Ignition wires
- Ignition coils
- O2 sensor
- AFM boot

The car passed smog with flying colors exactly a year ago to this day!!! But yesterday it failed. Prior to the test, I noticed that it idles funny. What do I mean? Well when I turn the car on, it idles at 600rpm and then goes up to 1000rpm before coming back down. and it does that forever, regardless of whether the engine is hot or cold. Is this a bad ICV or an intake leak? How do I test it?

Is high NOx and HC an indicator of a misfire? Are my ignition wires and/or coils done and need to be replaced? Is my oxygen sensor gone and need to be replaced? Where do I start? 

Thanks for your help gentlemen!

[romkasponka]

You should do diagnostic for your engine and you will know more. Otherwise you just spending your money for nothing...

[dueporte]

Hopefully you have resolved this. Wanted to mention I have had the rubber boot between afm and intake cracked on bottom as well as loose oxy sensor. Almost did not pass ca smog with o sensor not tight.

[hgrunt]

Bringing this one back from the dead, since I can't dig up anything else on search, and would like to keep everything in one place, in case it helps someone else out. Last time I smogged the car, I failed the 15 mpg test, with high HC and HOx. I replaced the oem cat with a Catco unit, and changed the 02 sensor, which led to passing with flying colors. The smog place even used a mirror to check my cat for the CARB EO number.

When I smogged today, I failed HC and NOx, with very similar numbers as my first smog, so I think I might have some kind of issue that was covered up temporarily with a fresh cat installed.

I found posts on other BMW forums specifically naming old/dirty/lazy injectors as a cause of high HC and NOx.

So here's what I'll try, and eventually report back to this thread on:
- Oil change, new spark plugs, the usual stuff
- Check my coils to make sure they're OK (I'm running a COP conversion kit)
- Install a set of reman'd 4-hole Bosch Type-3 injectors (PN 0280155700 )

And if anyone knows, what would be the symptoms of a failed intake boot and/or FPR?