[Halfwalker]

Dang it - my 94 just failed CT emissions. It's passed many times before, and passed well. There have been no mods, or rather, changes, to the config for the last several years.

94 TT OBD1
Apexi S-AFC
Apexi EVC-R
Stock twins

Test results ( result / permitted )

            Feb 2010                 Apr 2011

HC (ppm)    86 / 100                 153 / 100
CO %        0.07 / 0.53              0.40 / 0.53
NOx (ppm)   935 / 1167               881 / 1167

So Hydrocarbons blew to almost double the value, causing the FAIL. Carbon Monoxide levels jumped almost 7 times !

Car feels fine. Pulls cleanly, boosts smoothly to 15lbs on low EVC-R setting and 19lbs on high, just like it always does.

The techs at the testing center said the O2 sensor was the most likely culprit, so I'll yank that this weekend if I can get a replacement before then. Exhaust tip is sooty, but it's been like that since forever.

What else should I be looking for ?

D.

 

[Nick 95 6sp]

Before I got far enough to read that the techs suggested the O2 sensor, that would be my first guess, too.

 

[NotyMKIV]

how long has it been since changing the spark plugs? I noticed NOx went down that usually means your cylinder temps are going down caused by a rich condition that coupled with unburnt fuel (HC) leads me to believe of a faulty ignition system, how does the car idle after its been idling for a while? my spark plugs used to foul out after idling for too long due to my plug gap being to small in order to cope with high RPM and higher boost also switching to a colder plug can mess with things.

 

[Beau]

^ Very nice post.

try the O2 sensor, but also perhaps bring it with stock plug gaps & stock heat range just for the test.

 

[DinnerTime]

Check plugs, O2 sensor. If you can lean the car out, lower your boost setting and lean it out a little bit to pass.

 

[NotyMKIV]

i wouldnt worry about boost settings too much since the car will just be at cruising speeds on a smog dyno

 

[Halfwalker]

Yeah, they do the test at 25mph I think. Plugs are several years old, copper I-forget-the-number. Car idles fine, sometimes a tad high at 1000rpm, but usually around 700-800rpm. I do have a faulty coilpack (or two) though - get stuttering at high boost. Verified by swapping out with known good ones from a friend, it ran silk smooth, put mine back in, stutter at high boost again. Haven't gotten around to replacing them yet.

Hrm - there was a thread about coil packs here a while back - red ones ? Any experience with them ? I'll dig around for that thread.

Any preferences for a replacement O2 sensor ?

 

[Ryeno]

replace the plugs. cooper ones wear out super fast, like each oil change fast. o2 go on amazon and get the factory denso sensor.

 

[Halfwalker]

My bad on plugs - I put in NGK Iridiums about 18 months ago I think. Totally forgot about that.

 

[Halfwalker]

Hrm - ton of Denso O2 sensors out there. Any specific part number, or just go with a universal ?

Denso 234-4209 Universal Oxygen Sensor ($35)
Denso 234-4626 Oxygen Sensor ($60)

Only diff I can see from the photos is the wire length ...

 

[Ryeno]

234-4514 that's the no solder required direct swap sensor.

 

[NotyMKIV]

the red coil plugs you where referring to i believe are called super spark coil packs http://www.superspark.com.au/producttoyota.htm they are cheaper than OEM and supposedly a direct swap. haven't heard much about them though

 

[Halfwalker]

OK, O2 sensor arrived. Went to have a look at replacing it.

There's no way to bloody get to it. It's on the upper side of the downpipe (I'm stock twins with 3.5" DP and exhaust), no path to it from above, and only a contortionist could get to it from below. Even then, you couldn't see what you were doing because it's on the upper side. Can't even reach the wires where they attach to the plastic clips as they run forward to the plug.

Either I'm missing a simple trick/path, or I'm going to have to drop the exhaust. Ick.

 

[twinturbosupra94]

You other option would be to run ethanol just for the test. Just make sure its tuned properly and you should be all set.

 

[shenofjo]

old thread revival, just want to know if o2 sensor replacement worked. I cannot remove the stock sensor by myself right now either, but I just managed to install my NTK sensor into my WB location just 2-3 inches below the original spot. will see how my smog goes this week. btw, your numbers look very similar to mine in HC and CO.

 

[Halfwalker]

Old thread revival, again. Finally got around to putting in new O2 sensor, drove about 50m and put in 1/2gallon pure acetone on top of 3gallons of 93.

Passed. But just barely.

HC CO NOx
Limit 100 0.53% 1167ppm
Feb 2010 80 0.07% 935ppm PASS (look at dat CO level !)
Apr 2011 153 0.40% 831ppm FAIL due to HC
Aug 2016 98 0.31% 333ppm PASS (barely look at HC)

Something must have changed over the years. It used to pass no problems at all, then in 2011 blew the HC levels, probably due to the O2 sensor. But even with that new O2 sensor and acetone, it barely squeaked by.

Still have to pass 3 more years before the 25-year exemption kicks in. What should I be looking for ? Hrm, just thought, I've never changed the rear O2 sensor ...

 

[FastTurbo]

I have to pass somehow in a month... or you could let the registration lapse, get temp tags for $20, go fail emissions $20, and they will register the car for 2 years with a failed emissions slip.

 

[Biologist]

Man I thought this was FastTurbos thread. Ugh

 

[foreverpsycotic]

Man I thought this was FastTurbos thread. Ugh

Heh, he is almost as bad as I was with my setup. One day he might have that pile running.

 

[Halfwalker]

Well, I went from 2011 FAIL to now with no problems. The new PASS sheet I just got says last test was that 2011 one, so they didn't seem to mind the registration renewal a couple of years ago, or whenever the hell it was.

3 more years then no more damn emissions (if I stay in wonderful CT).