Failing Smog

[Digitac]

Hi everyone, I was wondering if I could get some advice. I'm trying to get my car to pass smog, but it appears to be running very lean. The "NO" levels are 3 to 4 times normal, and everything else is really low. My wideband gauge is usually maxxed at 18:1 at idle and low speed cruise. On the freeway it's a bit more normal running around 15 or 16:1 and under boost it drops down to 11 or richer. Any ideas as to how I can get the NO levels down? I already replaced the front O2 sensor, but that didn't seem to improve the issue. I haven't gotten any codes lately, but I'm thinking there might be something wrong with the EGR system or maybe my MAF? The shop even suggested a vacuum leak. If I can't get this fixed I'll have to leave the People's Republic of California (can't give up the car!).

[Tom @ Fast Forward]

I agree. Sounds like a vacuum leak. Any idea what your vacuum level is at idle?

[Digitac]

I finally had a chance to drive it yesterday and check the Vacuum. It's idling at 18-19 in. Hg. I remember you had a can or something that you'd spray around the engine and it would rev when it hit the leak. What was that stuff?

I hope it's not the seal between the supercharger and intake manifold. I had a heck of a time getting that off and on last time and I think I did a pretty good job of getting it sealed.

[Tom @ Fast Forward]

18-19 is normal. Not a vacuum leak then.

EGR can cause high NOx but should throw a CEL. How do the spark plugs look?

[Digitac]

Well, I'm at a hotel this week, and it's not the kind that would appreciate me pulling the plugs out in the valet area ;-) This weekend I'm going to clean the EGR and run some seafoam or water through the intake, so I'll pull the plugs at that point and take a look. Haven't gotten any EGR CELs in a while, but maybe it's just a little bit out of whack.
Thanks for confirming it's not a vacuum leak, that's good news.

[Digitac]

The plugs look fine. Not sure that cleaning the EGR tube did anything, it didn't look plugged in anyway. It's still running lean, though I've noticed it's primarily doing so when vacuum is higher than 8 or 9 inHG. Is it possible that a leak between the MAF and the throttle body could cause this? Is there enough vacuum there to actually matter? I'm not sure how much restriction the air filter causes.
I hate California some days..

[socal pat]

The plugs look fine. Not sure that cleaning the EGR tube did anything, it didn't look plugged in anyway. It's still running lean, though I've noticed it's primarily doing so when vacuum is higher than 8 or 9 inHG. Is it possible that a leak between the MAF and the throttle body could cause this? Is there enough vacuum there to actually matter? I'm not sure how much restriction the air filter causes.
I hate California some days..

Well at least we know the PC-pro is doing its job ;) A leak after the MAF would let in a bunch of unmetered air.... and that would mean lean.

[Tom @ Fast Forward]

You know, an air leak (no vacuum there) between the MAF and the TB could do it. That would get unmetered air but should not create any vacuum error. However, I would think that the O2 sensor should compensate as long as you are off boost??? I'm confused.