CA Smog/High HC's

[Fireman91186]

So after sitting for a while now I am in a place I can finally get the Cherokee back on the road. Bat as many of you know that is not always an east task here in California the land of the ridiculous smog Nazis.

So I took it to get smogged and my HC's are 1200 and my CO is 3.05.

What I have done is Changed oil, replace plugs and wires(gaped properly), new cat, new fuel filter, fresh tank of fuel, cleaned egr and rebuilt carb. All of this has brought my HC's down from 2200 to 1200 so progress is being made but not enough.

I am running out of ideas here. All i have left is possibly adjust the carb more (seems to be running a little lean). After that I am at a loss.

Anyone have any better ideas as to what I can do?

[carnuck]

Plugs are OEM or cooler? Go to Napa and get an IC12SB coil. Cut the stupid horseshoe connector off and replace it with eyes. Thermostat of correct temp cuts CO a lot. Do they show NOx reading? Is it IM240 testing? If so you can go online and "see" the test results as they did it. My son's failed because the tester manually downshifted at the end of the test and that was the only time it popped over the limit.
Carb too lean will cause misfire, but usually HCs are down and CO is way up. Did it fail only at the idle?

[letank]

What are the other values, O2 (to see if you are lean) , CO2.... at 1500 and 2500 rpm, you have enhanced test. Scan the results part if you can and post, it makes it easier to read.

As Jim said, probably misfire for the High HC (unburnt HC) and overly rich for the high CO.

I run champion 404, which are the stock plugs, and a TFI coil...

Is the power valve connected to manifold vacuum?

[carnuck]

Did they have the 2150 in '79?

[Stuka]

Either you are way rich LEAN or you have a misfire timing issues. Only Main reason for HC's being so high.

I would look into carb issues. Make sure your idle mixture is ok. When you rebuilt it, did you replace the power valve?

Also check your timing again, and make sure the vacuum advance is working right.

EDIT: Sorry posted this quick yesterday and did not recall correctly that high HC is caused by being too lean. The strike through text is my original text.

Sent from my iPhone 5S using Tapatalk

[ProTouring442]

Low CO and High HC = too lean

High CO and High HC = too rich

[babywag]

My guess...
The power valve that came in your rebuild kit is no good and it's just dumping fuel all the time.
Pretty common actually.
That or the valve isn't getting manifold vacuum to hold it closed, hose hooked back up to PV?

[kurtuleas]

I am in the same boat.... my numbers are close to passing, but the high NO at 15mph killed me.



I also failed the fuel tank pressure test....but I have NO IDEA why. I replaced the filler neck hose, the vent hose and all the vent line hoses. I think the guy just did not seal it well enough at the cap...

I have been told I either have a lean miss or maybe a vacuum issue..

[letank]

I am in the same boat.... my numbers are close to passing, but the high NO at 15mph killed me.



I also failed the fuel tank pressure test....but I have NO IDEA why. I replaced the filler neck hose, the vent hose and all the vent line hoses. I think the guy just did not seal it well enough at the cap...

I have been told I either have a lean miss or maybe a vacuum issue..

May be not the same boat. you have another problem, high NOx is either too lean -which is not your case, as the CO is close to the average- or non working EGR, but the Higher than normal HC could be a lean condition see graph below.. or a vacuum leak....


the diagram at the smog shop



The gas curve



and 10 years of smog test for the 85



The last test, the HC is almost failing... found a disconnected distributor hose after the test.... Ironically the previous test, I had worn out valve seals... it was a big fog on every restart... so last year for Ouray, I decided to replace the valve seals, the oil consumption dropped by half... but I almost failed smog.... Also I never changed the oil before the smog test... to see what are the normal values.... except for the last test...

Otherwise a good site for the lambda calculator so you know if you are rich or lean...

http://www.916smog.com/lambda-calculator.html


FOrgot the gas tank... check for rotten hoses between the gas tank and the charcoal canister.... there is a nice rubber hose between the gas tank and the transfer case that is exposed to the heat of the cat, the hose might be good, but the clamps might be holding dry rotten hose. The "check valve(s)" one on the front and one on the rear of the gas tank.... are supposed to let the fume move to the charcoal canister... I think that they are plain elbows, and could be compromised.... luckily mine are good...

Remember to have the smog tech sign on everything... if work is suggested... it has to be by a licensed smog technician... do not assume.... you need it in writting ... as when you reach the $500 you get a 2 year waiver from the state after visit to the smog referee..... I had to do that with the Honda civic.... the smog tech did the wrong diagnostic... but I followed the recommended repairs..... still failed.... and found a rotten hose on the back side of the intake manifold... $.50 and I passed the next round... upsetting... well... it is smog check and dealing with tech that are not really good analysts.... well I failed too... the spray of wd 40 did not work, because the hose is tucked under the intake manifold against the firewall.

[carnuck]

I am in the same boat.... my numbers are close to passing, but the high NO at 15mph killed me.



I also failed the fuel tank pressure test....but I have NO IDEA why. I replaced the filler neck hose, the vent hose and all the vent line hoses. I think the guy just did not seal it well enough at the cap...

I have been told I either have a lean miss or maybe a vacuum issue..

High NOx is timing too far advanced, allowing too high of combustion temps. Knock timing back about 4 degrees and NOx will drop like a rock.

[letank]

In Cal, we cannot lower by more than 3 degrees to the timing specs on the sticker which is checked by the smog tech.

[letank]

Forgot about the charcoal canister,

http://www.smogtips.com/charcoal.cfm

check the lines around the top and remember that those plastic nipples are very brittle.... especially the one with the cover that is labelled do not remove, there is a spring under the cover, and a rubber diaphragm that is usually rotten.

[kurtuleas]

but the canister should not matter becuase they seal the line between the canister and the tank when they test. correct?

[Stuka]

but the canister should not matter becuase they seal the line between the canister and the tank when they test. correct?

There is a valve in the canister that is vacuum operated that should shut off when the engine is not running. They should do the tank test with the engine off. If they do it with the engine on, it will fail for sure.

I know the smog place I go to also has a way of injecting smoke into the system so you can see where it comes out.

[kurtuleas]

but the canister should not matter becuase they seal the line between the canister and the tank when they test. correct?

There is a valve in the canister that is vacuum operated that should shut off when the engine is not running. They should do the tank test with the engine off. If they do it with the engine on, it will fail for sure.

.

Huh....


They did it with the engine running, but they put a clamp on the hose from the canister to the vent lines on the fuel tank to seal it off.

[Stuka]

but the canister should not matter becuase they seal the line between the canister and the tank when they test. correct?

There is a valve in the canister that is vacuum operated that should shut off when the engine is not running. They should do the tank test with the engine off. If they do it with the engine on, it will fail for sure.

.

Huh....


They did it with the engine running, but they put a clamp on the hose from the canister to the vent lines on the fuel tank to seal it off.

Clamping it off will work, although it technically means its not testing the charcoal canister. Which is to your aid, because for all you know its bad

[carnuck]

In Cal, we cannot lower by more than 3 degrees to the timing specs on the sticker which is checked by the smog tech.

You can change that by resetting timing till the reading is right and then adjusting idle to the correct speed/time.

[Fireman91186]

So I am back among the living (had a wisdom tooth pulled this week).

My hydro carbons are 1242

CO 3.05

CO2 12.8

NOX 41

[carnuck]

Is that the HC reading or the RPM it was checked at?

[Fireman91186]

That's the reading.

The RPM was 2500

That is my problem.

I have had to deal with plenty of vehicles and smog, but I have never had one this far off.