Dennis-Z28

iTrader: (1)

I failed by about 2x and they give you a list of things it could be such as cat., rich fuel, EGR, oxygen sensor, etc.

Would a brand new cat. cause it too? It was put on the same day but I did not have insurance to 'break' it in over days so only drove it for 1/2hr to get up to temperature. That day the exhaust was stinky (paints burning smell) but now it is normal.

No dummy lights were on so I doubt any sensors were bad.

camaropower88

sadly, HC doesnt tell much of the story. HC is RAW fuel, meaning it did not burn at all or begin to burn. Thats what CO is. CO is the byproduct of INCOMPLETE combustion. You can have excessive HC from either a rich or lean condition. You need the CO and O2 readings to actually tell lean or rich. O2 higher than the CO is lean, and CO higher than O2 is rich. Now on the emissions test sheet you get back it does not have an O2 reading. If you only failed for HC you most likely have a lean condition, sometimes depending on how severely lean you are you can also fail for Nox, and BARELY fail for CO as well, such as I did. Check for vaccuum leaks and check your fuel pressure, make sure your fuel system is good and you are getting enough fuel. Failing emissions is just an imbalance of the air/fuel ratio. Like i said you need O2 readings and CO to determine which way the air/fuel ratio is being altered so you have a starting point, whether that is diagnosing a lean or rich condition. Hope this helps at all.

gurkgurkgurk

we'll need the rest of the test results to have a better picture of your car. like NOx, CO, CO2. all that jazz

camaropower88

Dennis-Z28

iTrader: (1)

went again today after a couple hundred kms to break in the cat. FAIL (just barely)

Driving test:
HC = 35 (86 allow) PASS
CO = 0.10 (0.57 allow) PASS
NOx = 779 (852 allow) close PASS

Idle test:
HC = 84 (82 allow) FAIL
CO = 0.36 (0.50 allow) PASS


My last test before that my NOx was way down at 149 in the driving test but my HC in the idle was up at 101. No check engine codes so not sure where to start looking. Maybe the repair shop

Dennis-Z28

iTrader: (1)

2 years later and same thing. Pretty much every sensor is newish.

Try replacing the fuel pressure regulator? Suppose I can get the shop to test the pressure, etc. How do you know/test for a faulty injector?

Fred SS

iTrader: (3)

Have you checked your timing? I've heard that it will not pass if timing is advanced. Should be at 6 degrees BTDC.

Dennis-Z28

iTrader: (1)

I have done the timing with the wire disconnected to 6deg BTDC. Seems to be good.

Would a scan tool be very useful so that I can read sensor values? I was thinking the Innova 3120 ($150) or the Actron CP9190 ($270) but both are very expensive and seem more for ODBII anyways. Is there a cheaper option the does scan, and not just code reading (as I can do that with a jumper wire)?

Ohm tested all the injectors at 17.2 Ohms each. Just bought a new fuel reg diagphram. Possibly O2 sensor is fouled by previous valve seal leak despite it only has a 1000 or so miles on it.

paulo57509

Is the engine stock with all the emissions equipment intact and operational?

What are your current measured/allowed numbers?

How did you get it to pass two years ago?

Dennis-Z28

iTrader: (1)

Car is stock except Hooker shorty headers, Flowmaster cat back. Cat is a high flow Magnaflow though which does not help.

Results were a bit worse than 2 years ago. I never passed last time either, I just never drove the car for 2 years. This time:

HC (Driving): Allow=86, Avg=34, mine=49 [PASS, tiny bit high]
CO (Driving): Allow=0.57, Avg=0.08, mine=0.01 [PASS, very good]
NOx (Driving): Allow=852, Avg=125.5, mine=681 [PASS, barely]

HC (Idle): Allow=82, Avg=25, mine=113 [FAIL, miserably]
CO (Idle): Allow=0.50, Avg=0.02, mine=0.66 [FAIL]

Drove my car around that day and got 18mpg avg on a tank (13.3L/100k).

paulo57509

A scan tool might be helpful in reading what the mixture is at idle. Can't really say for certain.

Attached is a pretty good read on combustion and how converters work.

Too bad you don't have the numbers for all 5-gasses at idle and driving (HC, CO, CO2, O2 and NOx)

86T/A_Ram_Air

ok lets start with the basics here. check all of your ignition components. Plugs, wires, cap & rotor. you should be able to pass with a high flow cat. but you need to get it HOT or it won't work properly

sid rs91

gonna be so happy when they finally get rid of stupid aircare
mine failed too and been parked since
https://www.thirdgen.org/forums/tech...reading-s.html
post up this print out may give a better pic of whats going on .....its from their website.

jordanandrewkay

. I know it won't tell u why its not passing but I'm willing to bet if u bump timing down to either 2* or 0* and rev it to 2500 and hold it there for a FULL 5 minutes right before they pull it in you will more than likely pass. its too close not too. inspector for 3 years . don't worry timing is not an item of inspection. at least not in Texas.


Posted from Thirdgen.org App for Android

86T/A_Ram_Air

It's not that it is an item of inspection but it's that it effects the emissions output

jordanandrewkay

well yeah that's my point. pulling timing would help emissions. I meant if it passes after that ,u still won't know what was causing the high amount of hydro carbons. especially if it passed because then you are masking a problem by pulling timing. but IMHO I would rather be searching why its not passing ( in stock form ) with a good sticker on it.


Posted from Thirdgen.org App for Android

Dennis-Z28

iTrader: (1)

Threw a new O2 sensor on and cross my fingers.

MY87LT

iTrader: (2)

Hope you pass. I failed twice and then installed a new oxygen sensor and passed.

Dennis-Z28

iTrader: (1)

Got rained out. I could have done it but I like to make an enjoyable days cruise out of any day I put temp. insurance on.

I did break down and go to a shop though previously and they said O2 sensor was wonky and if that don't work then swap out my high flow cat for a regular one. I also put in a new fuel regulator as it looked leaky but after removing it the diaphragm was okay so doubt that did anything.

Maybe Saturday will shine some convertible rays.

IROCU2

Dennis did you make it to the emissions testing? If so did you everything go great?

Dennis-Z28

iTrader: (1)

Woo-hoo! I passed with the new O2 sensor. Everything was well below the limit except NOx on the driving portion which I got 851 out of 852 allowable (whew).