Heres a tough one about passing emissions...

[Mark B]

All right guys this is killing me. I still can’t get my car to pass emissions. I am on the brink of paying someone to pass the car for me. But I want to get some more advice and give it one more try before paying $100 to get it to pass. This is what has happened so far.

I stupidly removed my AIR equipment and replaced my stock cat with an Aftermarket High Flow Cat from Magnaflow. I took it to inspection and failed for CO%
SEE ATTEMPT #1

I then retarded the timing back to stock & dropped the fuel pressure. This fixed the CO% problem, but then my NOx skyrocketed. I figured that I leaned it out too much.
SEE ATTEMPT #2

I then raised the fuel pressure up a little to try to get it and pass again. But I didn’t seem to bring it up enough.
SEE ATTEMPT #3

I then raised the fuel pressure up some more and I got the exact oppsite of what I wanted. The NOx actually went back up a little.
SEE ATTEMPT #4

[94 formula]

Are you getting your cat warm enough. All the AIR equiptment is doing is pumping air into your cat to warm it up. Are you running your car long enough to get the cat heated up. Also have you done a good tune up lately? And have you tried going to an autoparts store and picking up a bottle of the stuff you add to your gas to make it pass an emmissions test?

[Mark B]

I drive the car on the highway for 30-45 minutes before taking it to the inspection station, I did a full tuneup about 5000 miles ago, I have not tried that bottled stuff from AutoZone

[Mike71]

if u have an auto shift it into 2nd and run up and down the street a few times before u get it tested ( sounds lame but it works) for a 5spd just dont shift up let the RPMs run high...helps my beater

[Kevin - Blown 95 TA]

The cat MIGHT be your problem. My Random cat with 2k miles on it flunked me twice, before I put the stock cat with 17k miles back on and passed with 2x better NOX 5x better CO and 10x better HC.

When I was troubleshooting the car I called a shop with a 5 gas analyzer and talked to the owner who seemed very knowledgable. He started talking about aftermarket cats and told me that they typically skimp on the precious metals needed to make the conversion work - Rhodium, Palladium, and Platinum are all expensive. Also the aftermarket cats only have to last 2 years compared to the 7 years or so a OEM cat has to work.

[Injuneer]

Did you try setting the timing and the fuel pressure to the mid-point of the settings used for Test 1 and Test 2? You definitely drove it from too rich to too way lean at Test #2. You may need an "in between setting". You returned the timing to stock after test #2... maybe use 1/2 the correction you used before test #2.

It also might be a little sensitive to how long you drive the car after you make the adjustments, but before you have it tested. It takes time for the long term fuel corrections to "develop", and you have to drive in the full range of load/rpm conditions that the emissions "drive cycle" uses. Perhaps after your first set of adjustments, you had the car tested soon after the adjustments, and the long term fuel corrections had not had a chance to respond fully to the lower fuel pressure.

As I recall from earlier posts, when you deleted the AIR system (required with the split bed cats on the 3rd Gens, since the pump has to run continuously), you also went with a high flow "monolithic" cat, that does not need the continuous air supply that the split bed cat with the intermediate air tube requires. Was that a cat selected by someone specifically for your car, or was it a generic "one size fits all" cat that you got from the I'net for low $$$? I'd be a little suspicious of really low cost cats, for exactly the reasons Kevin mentioned.