Scratching My Head: Failed NJ Emissions High CO & HC

[Dogydude5]

All right, so let me thank everybody in advance for helping me...

I've used the search button on the forums, but haven't read any posts that are very similar to my problems. I took my '91 Talon TSI AWD to get inspected last week and failed emissions horribly. As you can see from the title, I failed because of high HC and CO% readings. New Jersey standards are 100 ppm for HC and 0.50 for CO%. My readings were 9.6 for CO2%, 112 for HC, and 8.31 for CO%!

I decided to replace my air filter, spark plugs (gapped at .032), and o2 sensor. I took my car back for reinspection and this time my readings were 10.0 for CO2%, 142 for HC, and 7.78 for CO%. From the reading that I've done, I know that HC is unburnt fuel, CO is partially burnt fuel, and for my car below a 13.0% for CO2 is very rich. I took my car to a local shop to have them read the computer codes and take a look at the car and they told me that they performed a cylinder balance test and that I have low compression because one or more of my cylinders being out of balance. However, they couldn't provide me with figures for the compression, being that they did a balance test and not a compression test. They were quick to offer a valve job though and if necessary work on the block... Anyway, I'm not too sure about the low compression diagnosis they gave me and I am going to have a friend do a compression test on it this weekend. I took the catalytic converter off tonight to take a look at it, and it still seeems to be in good shape... no rattling, no sign of oil, just carbon deposits.

I was hoping that someone could offer some suggestions as to what they might think is causing these poor emission gas numbers. Any help is appreciated. Oh yeah, and I don't know if it has any relevance, but my coolant level light went on about 2 or 3 weeks ago. (This originally had me thinking about a possible broken head gasket, but my oil looks fine, there is no bluish-white smoke, no whitish substance on the exhaust tip, and no signs of leaking water under the engine.)

I was running 93 octance and I don't have any fuel upgrades or perfomance parts on the car yet, it's stock, except for my gauges. And while speaking about gauges, I have a narrowband A/F ratio gauge (I know it's crap and useless), but anyway, when I'm just cruising (not getting on it) the gauge still reads in the green L.E.D's (rich). At idle, the gauges oscillates (bounces back and forth) and when I get on it, it reads rich, but when I am just on a cruise it still reads rich. Sorry for writing so much, but I like being thorough and getting as much detail out as possible.

 

[srumel]

How long did you wait between installing the o2 sensor and getting it reinspected? The car needs to be driven a bit before the ECU "relearns" the fuel mixture. A quick way to get the ECU to relearn the fuel trims just disconnect your battery for a few minutes, reconnect, and drive!

Another possibility is that your TPS is out of adjustment. If you have a datalogger, you just need to adjust it until it reaches 10% with the car off and the accessories on.

Also, I could be wrong but I think that those A/F gauges can interfere with the o2 sensor's signal to the ECU in some cases. Just something to think about.

 

[DSM1G90]

Plugs are gapped to wide .. should be down to .28-.30 for starters. Thus being gapped that wide, there being slightly snuffed out on compression and not fully igniting the fuel causing unburnt fuel conditions which is shooting your reading up some.

Is youre EGR valve connected, or do you have a blockoff plate attached? If blocked off, that'll fail you right there..

Get those gaps down to turbo specs... Also, since you're in the stock range with a 6bolt and timing in the 5*BTDC, go down to 87 unleaded and get things close to factory stock specifications. That should get you cleaned up some.

 

[Dogydude5]

I gave the car a good 4 days or so between when I changed the o2 sensor and getting it reinspected, but I'll disconnect the battery today and see if that helps any. As for a datalogger, unfortunately somebody broke into my car a few months ago when I was down at school and stole it I hadn't thought of the gauge itself screwing up the o2 sensor's signal to the ECU, I'll definitely take a look into that.

I'll decrease the gap to .030 and see how that works out, but I'm sure my EGR valve is connected. I haven't altered any of the emission related components on the car and I passed inspection two years ago when I first bought the car. What would running 87 octance do... How much would it help?

 

[crimsondragon]

As fuel octane increase, contrary to the belief, the fuel is more "dirty." There are a lot more chemicals and other things to make it resist detonation. I laugh every time I hear somebody say they're going to clean the engine by putting in premium. The 87 will also make you run hotter causing a cleaner burn. However, do it when you're almost out of gas and only fill up enough for the inspection. And do not get into boost. You'll be looking at more trouble than it's worth. Also gap the spark plugs to .028"
I'd replace that cat if it hasn't been replaced since it rolled off the factory as well.

 

[91dsmgsx]

The haynes manual i have for 1g dsms says the spark plug gap should be .032in, just wondering why changeing the gap to something else other than service specs should be done?

 

[Bubbs Malone]

Just a thought, I talked with the tech after failing the Emissions test in CA this past year. He told me the best way to lower emmisions would be a CAT or Carbon cleaning. I changed my Cat, before and after readings:

%CO2
14.5/14.6 (15MPH)
14.5/14.3 (25MPH)

&O2 "
0.0/.1
0.0/.6

HC (PPM) "
101/14
37/8

CO (%) "
.16/.3
.06/0.0

NO "
224/15
381/42

The HC was over the limit in the first test
I hope this helps some. Oh, the original cat had over 200K miles on it, I think I found the problem.

 

[Dogydude5]

Thanks, I'll definitely take another look at the cat for sure... I'm just still unsure why the car is running so rich and this is what is causing me to steer away from the cat and toward something fuel related or electrical. I'm going to spend most of tomorrow visually inspecting the car and the better half of the weekend tackling all possibilities that I can think of. But as I said, I will definitely look into replacing the cat (but in comparison to the numbers above... my CO readings on my second try were still 48x the worst readings above). I guess I'm just wondering if anybody had any thoughts on why the car would be running so rich with the conditions I originally described?

Oh and by the way, I regapped the plugs to .028 to see if that would help any, made sure the FPR was working properly, and disconnected the narrowband to see if the ECU would get a better read from the o2 (possible wiring issues?). I do believe that the car is running slightly better, but not enough to help when it comes to inspection time.