Andrew, stock cat is three-way unit, if you have replaced it with an aftermarket downpipe and cat, it may be that the exhaust is cooling off too much before it reaches the cat at low eng. speeds. The stock downpipe is double walled to keep as much heat in the exhaust as possible, the aftermarket pipes are not. I had a problem with just this a couple of days ago, make sure the engine is fully warmed up before the test, if you have to sit and wait for the test, rev the engine to 3,000 rpm or so for a minute before the test and make sure they do not run the tests in too high a gear, the cars are geared too tall to run the 15 mph test in 2nd and the 25mph test in 3rd. Good luck Mark

 

The cat he's using was a stock pipe rebuilt with new guts. I know I sold it to him. It has a tag welded to it specifying the rebuilder's codes that make it legal. It hadn't been used since the rebuild, and my identically rebuilt cat works just fine. I just happened to end up with two of them.

FWIW, Andrew and I've traded some long emails trying to nail down his problem. He's passing everything but NOx at 15mph. I suspect a vacuum leak. He's going to try to do a thorough check of his system for leaks. Just today I tried to identify a list of "the usual suspects".

The only other thing I can think of, is whether his TPS is adjusted correctly. That was the one thing that kept me from passing until I got it right.

 

Really? This is the first I've heard of the sniffer going away in metro NYC (sadly, the more stringent tests apply to westchester county and most of long island too). It would be a delight if I no longer had to worry about the car passing!

 

That's what I hear. Some have said that the city is going to follow upstate and go with this OBDII scan instead of a sniffer test. But, for the large trucks and whatnot, I guess they will still do a sniffer test.

 

Kragen has this stuff in a blue box that they sell for $6.99, and they guarantee you, under any conditions, to pass smog.

 

The place I use in Burbank by chance the owner a young guy in his late 20's used to own a 944 turbo. He LOVES these cars! It's just north of western on glenoaks on the left hand side if your traveling north.

He always runs it unhooked for me to see if it will pass and I really don't think a maf is going to be an issue there. He'll probably just get excited.

There is also a porsche mechanic within 1/2 a mile of this place, the mechanic uses him for all his smogs and spent quite a bit of time fiddling with mine and only charged me $100

http://www.petesautotech.net/HTML/new_used.html

call him up, maybe he can help you out