Emissions Fail

[davidp94]

My 1990 Nissan 300zx failed emissions. Before it was tested it sat for 3 years with a seized engine. Thereafter, I proceeded to drop a newer VG30DE in it.

After the swap, I brought it for an emissions test. It was done in january and in Ontario and that means its cold out. I don't think I let the car run enough to heat the catalyst adequately but anyways based on these results why do you think it failed?

The results are:

ASM 2525 TEST Curb Idle Test

HC ppm HC ppm
Limit: 0057 Reading: 0168 Limit: 0200 Reading: 0446

CO% CO%
Limit: 00.32 Reading: 00.68 Limit: 1.00 Reading: 02.75

NO ppm
Limit: 632 Reading: 511 (I passed this portion of the test) They also did not test for NO ppm on the Curb Idle Test.

Based on these numbers can anyone identify why they think I failed? Could it be as simple as purchasing a fuel cleaner?

I'd appreciate any insight I can get.

[davidp94]

I realize the numbers kind of got jumbled together. The first set of numbers (limit and reading) are for the ASM 2525 Test and the last set of numbers (limit and reading) are for the Curb Idle Test

[Ace2cool]

Honestly, sounds like bad cats.

[DCaff300ZX]

If you get a free re-test be sure to run it on the freeway for 15-20 minutes beforehand, and if it fails again look at the cats and AIV's (responsible for allowing some air into the exhaust to "thin" exhaust emissions) for problems. Next up is injectors and fuel system, the FSM has a section for testing the various areas needing attention.
That's about the best we can do from here...

[NolimitZ32]

It looks like your car is just dumping way too much fuel in across the board, you may be looking at work O2 sensors, or a filthy MAF, I've never seen a car fail every single test both at low load and high load. Unless it was a fire-breathing, fuel spitting monster with a carb and massive cam.

[davidp94]

How easy is it to go about getting at the O2 sensors on an NA?
Ill probbaly just purchase new ones and install. They aren't that expensive anyways.

I may just go ahead and clean the MAF when I install my pop charger (still have the stock box

[Ace2cool]

Getting to them isn't the problem. Getting them out is. Lots of rust and heat cycles tends to make things not want to come out.

[NolimitZ32]

Getting to them required a long extension and a universal joint, from the bottom you will have more luck with an offset O2 socket, from the top I believe you can use either. the reason for the long extension is to you can get the leverage to brake it loose, after that you shouldn't have too much trouble threading it out.

[davidp94]

Okay and out of curiosity, how does removing the hose from the fuel damper decrease my HC and CO levels? What happens when I remove it?

Or pulling the small hose that goes to AIV solenoid?

[NolimitZ32]

I'm not sure about the fuel damper, if you pull the vacuum hose off your regulator your car doesn't adjust for higher vacuum so you basically cause a lean condition thereby lowering your HC. I believe, and don't quote me on this as it's been some time but Lean causes your NOx to go up so its always a trade-off. As for the AIVs I will tell you honestly, since I never had to deal with them I never really paid attention to how exactly the system works. But I would Imagine the premise is similar only instead of controlling fuel to the engine it controls air to the cats.

[Ace2cool]

It injects air into the exhaust system. Basically Nissan figured they would cheat emissions, and then later realized they didn't need it in the first place, so they removed it.

[Z-owned]

Well I would suggest finding the issues and fixing them if you want something that may help you pass look into CRC guaranteed to pass. You dump a bottle into a near empty tank and fill up then drive until it's about empty again, fill up and go test. I have passed multiple cars now without any cats including my Z with it.