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Smog test, high HC

P

Paul S

NAXJA Member #103
Location
Woodland Hills, CA
Passed everyting except HC at 25 mph/1692 rpm (passed HC at 15 mph/1651 rpm). At 25 mph HC was 71, max allowable is 38.
Prior to smog I put in a new Cat., changed the oil, plugs, air filter & fuel filter.

Any ideas as to how to lower HC?

It's a 96 with 115,000 miles.

Paul
 
First question would be, did you get an OBDII compliant catalytic converter? HC is unburned fuel, which can be caused by a number of things, most of which you already changed. The o2 sensor is usually the culprit in cases where everything seems to be running OK.
 
Here are several causes of high HC levels, as taken from my emission controls textbook:
-ignition system misfiring
-improper ignition timing
-excessively lean or rich air/fuel ratio
-low cylinder compression
-defective valves, guides or lifters
-defective rings, pistons or cylinders
-vacuum leaks
-plugged PCV system
-stuck open heat riser valve
-AIR (air injection reactor) pump inoperative or disconnected
-engine oil diluted with gasoline
 
Bryan C. said:
First question would be, did you get an OBDII compliant catalytic converter? HC is unburned fuel, which can be caused by a number of things, most of which you already changed. The o2 sensor is usually the culprit in cases where everything seems to be running OK.
Click to expand...

I did not get an OBD2 Cat., but I've replaced the Cat. every 2 years prior to smog with the same little Cat. that I put on last week. Having said that, the smog guy said that the restrictions tightend just last month & that had I taken the test last month I would have passed, he added that if I got an OBD2 Cat., or at least a bigger Cat., I'd probably pass now.
Do you think a new o2 sensor would make the small difference needed? I hate to put another new Cat. on if I can avoid it.

Paul
 
RenegadeStang said:
Here are several causes of high HC levels, as taken from my emission controls textbook:
-ignition system misfiring
-improper ignition timing
-excessively lean or rich air/fuel ratio
-low cylinder compression
-defective valves, guides or lifters
-defective rings, pistons or cylinders
-vacuum leaks
-plugged PCV system
-stuck open heat riser valve
-AIR (air injection reactor) pump inoperative or disconnected
-engine oil diluted with gasoline
Click to expand...

I think I'll just go shoot it & put it out of it's misery :confused1

Paul
 
ChuckD said:
You can try this stuff. :D

www.passsmog.com

The high NOX formula may have helped me with my test 4 weeks ago.
Click to expand...


Faking it always works best. :) That stuff might be worth a try.

I hear you on the cat Paul, no need to spend more money on something that will get smashed up anyways. The o2 might work, but it is always a crapshoot. Honestly I think you are this close, try the snake oil and see what happens.
 
ChuckD said:
You can try this stuff. :D

www.passsmog.com

The high NOX formula may have helped me with my test 4 weeks ago.
Click to expand...

The problem with this stuff is that I can't drive on road to run out the tank. Or maybe that's a bonus, I'll just explain to wifey that I have to head out to JV this weekend in order to do my thing for clean air, it shouldn't even count as a vacation weekend:)

I'll give it a try, thanks.

Paul
 
Replaced my little 9" cat with a $60 14" cat. I didn't spring for the OBD2 as it was 3 X the $ & at this point I didn't really care if I passed or not.
Anyway, the larger cat did the trick, HC's dropped to 26.

Paul
 
i had high HC's and i used 2 OZS of pure acetone in my tank, with 10 gallons of Shell 87 and it passed like a new car. Mine is a 93 and failed smog with high HC's and NOX. i replaced the O2 sensor and added a bit of acetone and i was all set to pass.

good luck!
 
OK! my turn :dunno:

I got it smogged and here are the results:

FileHandler.ashx


The XJ is a '94 with 159,000 miles on it. It uses 87 octane fuel (does that matter?). Brand New Huge Cat and the O2 sensor is 1 Year old. It is all stock EXCEPT for the gay ass Rocket Parts Air Tube (CARB approved though).

FileHandler.ashx


Air filter was a tad dirty but I didn't think it was that bad at least by looking at it.

HC and CO were like it is a new car. NOX was out of control though. O2 was practically non existent. It was at a 'TEST ONLY' center and the tech said I should clean the air filter and replace the O2 sensor.

Thoughts?
 
cracker said:
NOX was out of control though. O2 was practically non existent. It was at a 'TEST ONLY' center and the tech said I should clean the air filter and replace the O2 sensor.

Thoughts?
Click to expand...

Ha ha.
 
Product called RXP can be picked up at most Autozones and similar places. I added it to my fuel tank a day or two before i knew i was going through inspection. On EVERY car i have done this two, the emissions results were nearly ZERO on everything. If I didn't see it with my own eyes, I wouldnt have believed it. 6 bucks well spent.
 
Two thing should fix this...smaller tires is number one. Big tires drastically raises NOx. Even with 35's mine is very close to failing on NOx...gearing doesn't matter. Try to find some 33's to borrow. Second, get it checked in the coldest wettest weather you can find. Moisture in the air lowers NOx and a cooler running motor lowers NOx. Try not to get the motor too hot before the test.
 
I had the same issue with my last jeep a few years back. o2 sensor fixed it.. You can go to Kragen and they will let you use the computer to see if it is sending any codes. My check engine light was not on but when I hooked it up it said o2 sensor. Also one of the smog guys said to take it down the freeway and get her hot before the test. I wish you look and hope some of this will be useful
 
BRADFORDXJ said:
I had the same issue with my last jeep a few years back. o2 sensor fixed it.. You can go to Kragen and they will let you use the computer to see if it is sending any codes. My check engine light was not on but when I hooked it up it said o2 sensor. Also one of the smog guys said to take it down the freeway and get her hot before the test. I wish you look and hope some of this will be useful
Click to expand...

I am not tripping any codes that I know of. The check engine light used to come on occasionally when I had a couple of cracks in my header though but those got all welded up. Code was 21 I think which said 02 sensor (or what ever the one of the Codes for the 02 sensor were).

-Avery
 
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