Extremely high emissions readings

[sbZ]

So I bought my 1993 300zx na last weekend. Went to get it registered and found out i had failed a few months earlier, so i went and got it tested again. The readings were off the charts! (most current readings below) I was hoping it just needed a little tune up or something so I replaced the spark plugs and changed the oil. Tested again and still off the charts. So I took some time and looked it over and did some research. The car had a strong smell of gas and a rough idle so I replaced the passenger side 02 sensor and cleaned the connectors of the coolant temp sensor (which was not working correctly). The gas smell is gone and the idle is much better now but after testing again the reading is still extremely high! I'm not really sure where to go from here so I come to yall. please point me in the right direction!

Here is the most recent readings (from like 45 minutes ago)

[t.mcginley.jr]

What is the condition of your cats? Does the exhaust smell funny?

[sbZ]

I cant really smell anything from the exhaust anymore but my sense of smell is sub-par to say the least. Also, I forgot to mention that i did the ecu diagnostic after i replaced the 02 and fixed the coolant temp sensor and it gave me the 55 "all good" code... I'm guessing it must be the cats if all the sensors are functioning properly. Anyone else have any idea? I cant weld so I would hate to pay a shop to replace the cats only to find out that they are not the problem.

[nissanfreak12]

With numbers that high, it looks like your cats are toast or was gutted by the previous owner. That will cause your numbers high like they are. My money is the previous owner gutted the cats, bad cats would make the car run horrible but the numbers would be a little better.

Curiousity, you said you replaced the spark plugs, what plugs did you use?

[sbZ]

Well the car is all stock and has cats on it so I guess they're just toast. I used ngk plugs from advance.

[nissanfreak12]

If you got the NGK from Advance, I can pretty much tell you you have the wrong plug. the Z's use a very specific plug, the run of the mill car auto parts stores do not carry them, period. The ones the parts store sells is too short. It may feel like it is running ok, but it could cause the car to misfire, NOT COMPLETELY COMBUST THE FUEL, detonation, etc. The correct ones for the NA are PFR6G-11. The TT ones are PFR6B-11B(stock). These usually run about $9-$11 per plug.

This could have some of the reasons why the emissions was so high. Also, just because the car is all stock does not mean the previous owner did not gut the cats or had someone do it for them. Best thing you can do is either take them off and look into them. The cats are the main source of the emissions.

[skywhine]

If you got the NGK from Advance, I can pretty much tell you you have the wrong plug. the Z's use a very specific plug, the run of the mill car auto parts stores do not carry them, period. The ones the parts store sells is too short. It may feel like it is running ok, but it could cause the car to misfire, NOT COMPLETELY COMBUST THE FUEL, detonation, etc. The correct ones for the NA are PFR6G-11. The TT ones are PFR6B-11B(stock). These usually run about $9-$11 per plug.
.

This is more opinion than fact. No offence. You are coreecet on that plug being the plug nissan isntalled and recomends you use, but that doesn't mean it wont opperate properly. Personnaly, i run the standard v grove plugs in my Z (along with the other turbo cars i have owned) and never had a problem, other than having to replace them after 8-10,000 miles as they ware out super fast. This is just a personall preferance. About 4 years ago i had a local tuner prove to me he could prevent detenation at higher boost levels (With proper AFR) on a dyno by removing the platinum tipped plug. All we could think was that the platinum tipped plug retained heat more so than the copper core plug.

IIRC the plug i run is FR6_-11 thus reataing most of the qualities of the OE plug, minus the platinum tip. This also allows for adjustment of the gap, Higher boost levels require a smaller gap. You cant adjust the platinum tip as you can destroy the tip. Its also nice that the v groves cost $2.99 each rather than $10 each.

So long story short: As long as you went with an NGK product its not going to create the numbers you provided. As far as a diagnosis of your car, im not able to do so over the internet. Take it to a local emissions certified shop and have them diagnose it, Spend $150 in the process and if it still wont pass emissions they will sign a waiver stating you attempeted to fix the problem and you become emissions exempt for that session. (At least in Washington, sorry i didnt look where you were from prior to writing this).

[sbZ]

I know the plugs are not the cause of the problem as the car failed before I changed them. However I did just go check them and they are bkr5es-11 so ill be changing them again soon...

Edit: Also, the emissions guy told me last time I was there that it was $800 to be exempt. He has me down for $150 already. I'm not really trying to reach the 800 mark just to pass emissions though lol

[t.mcginley.jr]

If the cats are stock then they are probably toast, usually from age and running rich will toast them faster. You can get 2 Magnaflow hi-flow cats on ebay for around $68 each and an exhaust shop should be able to swap them out for less than $100 (cut old ones out, weld new ones in).

magnaflow cats:
http://www.ebay.com/itm/350585542691?ss ... 3274wt_952

[Z31toZ32]

If you got the NGK from Advance, I can pretty much tell you you have the wrong plug. the Z's use a very specific plug, the run of the mill car auto parts stores do not carry them, period. The ones the parts store sells is too short. It may feel like it is running ok, but it could cause the car to misfire, NOT COMPLETELY COMBUST THE FUEL, detonation, etc. The correct ones for the NA are PFR6G-11. The TT ones are PFR6B-11B(stock). These usually run about $9-$11 per plug.
.

This is more opinion than fact. No offence. You are coreecet on that plug being the plug nissan isntalled and recomends you use, but that doesn't mean it wont opperate properly. Personnaly, i run the standard v grove plugs in my Z (along with the other turbo cars i have owned) and never had a problem, other than having to replace them after 8-10,000 miles as they ware out super fast. This is just a personall preferance. About 4 years ago i had a local tuner prove to me he could prevent detenation at higher boost levels (With proper AFR) on a dyno by removing the platinum tipped plug. All we could think was that the platinum tipped plug retained heat more so than the copper core plug.

IIRC the plug i run is FR6_-11 thus reataing most of the qualities of the OE plug, minus the platinum tip. This also allows for adjustment of the gap, Higher boost levels require a smaller gap. You cant adjust the platinum tip as you can destroy the tip. Its also nice that the v groves cost $2.99 each rather than $10 each.

So long story short: As long as you went with an NGK product its not going to create the numbers you provided. As far as a diagnosis of your car, im not able to do so over the internet. Take it to a local emissions certified shop and have them diagnose it, Spend $150 in the process and if it still wont pass emissions they will sign a waiver stating you attempeted to fix the problem and you become emissions exempt for that session. (At least in Washington, sorry i didnt look where you were from prior to writing this).

well i have to trump the newb to the forum at this point. i know skywhine is an ase certified mechanic, which is highly respectable, but you can ask about anyone on here that has brought their z to a mechanic - they cant figure a thing out with the z's unless they have experience with the car and its querks. that is a strong contributing factor in the ridiculous network of underground z mechanics in cities across the us. they are really specific and a pain in the a**. anyway what nissan freak said was correct. the cars should only be ran with the plugs he listed above. only exception is running a super high horsepower tt application.

i'd run the correct plugs and re-run. if you still fail, there are some tricks to pass emissions, starting with this one: http://www.300zx-twinturbo.com/tech/co/co.html. there are some members on here that have passed with it after failing miserably.

[t.mcginley.jr]

There's also some kind of cats that have an "air-gap" which sucks in fresh air right at the cat so the emissions readings go way down

[sbZ]

i'd run the correct plugs and re-run. if you still fail, there are some tricks to pass emissions, starting with this one: http://www.300zx-twinturbo.com/tech/co/co.html. there are some members on here that have passed with it after failing miserably.

Yeah I'm gonna change the cats and plugs. I've seen that trick but I just can't convince myself that it would drop it down enough to pass.

[IonZ32]

You dont live in California however, CA smog machines can tell when there is too much oxygen or air being pulled in. I wouldnt be suprised if other states have them as well. The machine will say "dilution" when this occurs and will stop the sniffer test. So I would avoid the "air gap" cats. The same occurs when there is an exhaust leak. I ran into that problem when smogging my friend's Honda. We had to fix the leak before continuing.

[t.mcginley.jr]

You dont live in California however, CA smog machines can tell when there is too much oxygen or air being pulled in. I wouldnt be suprised if other states have them as well. The machine will say "dilution" when this occurs and will stop the sniffer test. So I would avoid the "air gap" cats. The same occurs when there is an exhaust leak. I ran into that problem when smogging my friend's Honda. We had to fix the leak before continuing.

Damn just when you thought there was a workaround...