I failed my local emissions test recently.

Oddly usually when I fail, I fail on NOX or HC.

This time I was off on both.

Nox Allowable is 878 I was 2218
HC Allowable is 123 I was 195

I've never had a car fail on Both a Hydro Carbon Reading..and NOX.

I have already replaced
1-Plugs
2-Wires
3-Distributor Cap
4-Bad Injectors
5-Cleaned K&N Filter

Only thing I haven't checked yet is the timing, which we had pulled the distributor out for another issue but replaced back based on our marks, but based on the lack of power now I wonder if I am a tooth off or retarding to much.

Anyways any thoughts guys? I might throw a cat on there too while I am at it.

Thanks!

 

One other thing that I noticed which might have no bearing on this. When I removed the fuel cap there was allot of pressure released. I normally see this when the car is really low on gas but its just a tick below 1/4 of a tank. I reinstalled the gas cap, and removed 3-5 minutes later for the gas cap test..and the same thing tons of pressure released.

Either my gas guage is off, or something else is causing this?

 

I don't know what causes this, but I often get this no matter how much gas I have left in the tank. This has happened to my last two maximas I had.

 

Forgot to mention also have replaced the Coolant Temp Sensor.

 

I recently failed my emissions test and here are the data:

HC 164
NOX 764
CO 0.64

The shop suggested my catalytic was bad so I went and replaced it and passed, not sure if you have the same problem because mine was high on HC and CO, the shop told me if I was high on HC and NOX maybe could be EGR related problem, I'm no expert on that matter I'm just sharing my experience.

 

HC---> Loss of ignition
CO---> Rich mixture condition
Nox--> Combustion chamber temp above 2500 F

A cylinder misfire also causes high HC and retarded timing also causes the HC to go up with CO..whats ur CO readings?...to much advanced timing causes the Nox to go up and HC and CO goes down...so u gotta check ur timing first...also check ur PCV valve cuz it controls the HC emissions from the crank case of the engine...

if ur engine is running hot or something is making it run hotter ur Nox will go up. Lean air fuel mixture causes the Nox to go up also and it could be cuz of restricted fuel system...check ur EGR if its working that will cause the Nox to go up too cuz an EGR failure will not only cause excess NOx, back up strategies will often entail enriching da mixture or retarding the timing. This in turn increases HC and CO emissions...and at the end jus change the Cat if u r not sure if its working properly or not....also run the ECU test to see if there is any codes...

 

Good luck, it's a struggle for me every single year to get my car to pass emissions. It fails on the first test every single time, and then I have to do a BUNCH of tinkering with it to get it to just BARELY squeak by. I wouldn't be surprised if I can't get it to pass at all this year. I think I'll retard the timing way down and see how that does. That's what my brother had to do on his old Civic to get it to pass

Also, it's normal for the tank to noticeably release pressure when you remove the cap. When you remove the cap and that DOESN'T happen, you probably have a faulty gas cap (and will fail that part of the test).

 

My CO is rock solid .36 out of a .51 allowed.

I brought the car home, did a little seafoam to clear any combustion junk since I have done that yet. Got it done..smoked up half the city I think.

I'm wondering if the engine is trying to compensate for some bad injectors. I just checked the back three since I am noticing a misfire at idle sometimes again. I got two that read between 15-18Ohms, all the others are in the 13's.

"I'm just frustrated. Had to put two new tires on her only because no one in town is willing to mount used tires now I had bought a nice set of Michelins with 7/32's MXV4's at that. So I had to just buy two new fronts. Then I fail emissions today, and when I roll up my window at the emissions place something pops in the door and then the window falls back into the door. Now its about to thunderstorm and I have a trash bag keeping the monsoon out

Bad day...bad month.
Ok I'm done with the vent"

 

Both my cars do this. I do not think it matters if it is full or empty. I only remove the cap when I fill up, but sometimes I fill up with half a tank and it still releases pressure.

 

this is a good thing. it means the gas tank is sealed. as it should be. if you are leaking fumes, you waste gas (among other things).

 

u got it

 

another way to reduce CO emissions temporarily is to toss in some alchohol.

 

Change your oil and filter then warm up the car and go to the emission station!

 

Check the vacuum lines going to/from the charcoal canister, replace any which look worn or feel stiff. I just went through something similar with the benz, fuel evap vacuum line was leaking.

 

what are emissions?
(I don't have any here)

Seriously, though. I would look into your injectors and timing. Use a timing light, not just your old marks.

I think the stuff already posted covered most of the possibilities.