Ca smog fail. Help!

L

ljobbins

NAXJA Forum User
NAXJA Member
Location
SD County
Cheap xj buy turned nightmare. 1995 4.0 auto bone stock. New plugs, wires, cap, rotor, belt, refreshed grounds and now cooling system.
Failed smog first time due to hi NO at 25mph. After the first test I changed every part of the cooling system due to it creeping up in temp while on the test and driving home. It now runs at 195-200 degrees and the cooling system is perfect again. I also changed the catalytic converter(walker ca legal) and o2 sensor to ngk brand. It idles and runs perfectly(except in the eyes of CARB). New smog test today and every number dropped except NO at 25mph and that actually went up from the first test. Before the test I ran it for about 45 minutes to warm it up. What’s going on? First and second test results.
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Ive been advancing and retarding my timing just a tad on my stroker to pass smog the last few years.
you may also need to just get her HOT. before the test.
 
blu3fan said:
Ive been advancing and retarding my timing just a tad on my stroker to pass smog the last few years.
you may also need to just get her HOT. before the test.
Click to expand...


How can I know if that is affecting my NO? Like if I do change the timing, how can I tell if that is changing my smog output for better or worse?


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You should clean the carbon off the top of the pistons with Seafoam thru the intake vacuum line. Start it and suck up a few ounces thru the brake vacuum booster inlet on the manifold and let it sit after you shut it off immediately. It might die when sucking in the seafoam thats ok let it sit for 15 minutes. When you start it up it will smoke bad thats all the carbon burning off. TAKE YOUR NEW O2 SENSOR OUT 1ST AND PUT THE OLD IN SO YOU WONT CONTAMINATE IT,
 
my2monkeys said:
You should clean the carbon off the top of the pistons with Seafoam thru the intake vacuum line. Start it and suck up a few ounces thru the brake vacuum booster inlet on the manifold and let it sit after you shut it off immediately. It might die when sucking in the seafoam thats ok let it sit for 15 minutes. When you start it up it will smoke bad thats all the carbon burning off. TAKE YOUR NEW O2 SENSOR OUT 1ST AND PUT THE OLD IN SO YOU WONT CONTAMINATE IT,
Click to expand...

Ive always been worried of this clogging up the cat if there is a lot of carbon. Am I wrong?
 
note the article indicates a high temp as a cause of NOx. lean running can cause this, but your O2 value of zero indicates you are not lean. however that zero O2 value is after the cat, and a good new cat can clean up a lot of sins in the motor. say one cylinder is lean do to intake leak, and the O2 sender senses the lean burn and compensates by enriching all cylinders, You do have high end of limit HC so that might indicate that, given a new cat. so this might be sign of lean on one or more cylinder and rich on the rest. for this do an intake leak test use a smoke machine or spray aerosol flammable carb cleaner tests for intake leaks, easy and quick to do. lets make sure we dont have an intake leak, that is low hanging fruit, check it.

you may also be running hot on all of them still, check you coolant temp with an independent known good gage.

you may also have the carbon build up in cylinder, which raises the compression ratio and causes more heat, specially if using low octane fuel. for this a de carbon process can be done, or retest with a tank full,of high test fuel if you are currently running low grade. high test fuel will lower temps if the cause is high compression, but the real fix is de carbonization.

for me on my 1990 I got with a brand new cat...

15 mph CO2 15.5% O2 11.5%, HC 2 ppm, CO 0.02 %, NOx 0 ppm
25 mph CO2 15.3%, O2 9.5%, HC 4 ppm, CO 0.05%, NOx 0 ppm

of course they can also sniff the exhaust before the cat if there is a port for that, then you can find out what the motor is really producing.

anyway, intake leak test is easy nd cheap, get that done, if no leaks, then consider decarbonization, perhaps. a lot of carbon build up can also cause high compresion readings, but that can be masked by worn rings.
 
First off I would pull all the plugs and do a plug inspection/reading on them. Just for grins, while they are out, I would run a compression test. No big reason for this other than it is quick and easy with the plugs out and will tell you a lot about the overall health of the engine. It will show up a leaky head gasket in most cases.

I have never seen a 0% on O2 before. I would call the validity of the test into question.
 
I got 0 for o2 on both tests. First test was with original o2 sensor and cat. If the machine was working right then swapping o2 and cat didn’t absorb any extra o2 that didn’t exist in the first test. And i can’t work on the car for about a week, but I’ll check the intake and try to de carbon the engine if there is any carbon.
 
old_man said:
<snip>

I have never seen a 0% on O2 before. I would call the validity of the test into question.
Click to expand...


My '88 was just tested with 0.0 %O2. Mine failed so far due to high HC and CO.
 
Have you checked for exhaust and intake leaks? I couldn't even hear mine an found a small crack in the header. The smog tech(young kid with good hearing)told me to check it.I have had no problems since then passing CA smog laws
 
Sorry- forgot about this post.
I advanced my timing by cutting the ears of my distributor and manually moving it.
Yes this is not a full timing advance as its controlled 1/2 way by the cps. but I barely pass w/ mine on 91. so I move it like 3-5 degrees- worked 3 smogs in a row now :)
Flame me all you want about this post- but it works danmit. just tricking a computer into running leaner/richer.

Don't go that extreme as ur stock.
get a propane torch/smoke and start checking for air leaks 1st.
aside from that- check basics.
smog checkup on NOX = Ur running lean.

ideas?
Car too hot. (XJ's are notorious for getting too hot to pass smog. I go on a Cold morning First thing AM. Run the car for 15mins prior to heat the cat..)

Cat too cold.
Not enough compression.
Not enough fuel.
U said spark is good. so grounds?

That's all I got lol
 
blu3fan said:
ideas?
Car too hot. (XJ's are notorious for getting too hot to pass smog. I go on a Cold morning First thing AM. Run the car for 15mins prior to heat the cat..)
Click to expand...

Notorious - says who? I smog mine in July and deliberately sit and idle to get as hot as possible. Passes with flying colors every time.
 
Ronbo said:
Notorious - says who? I smog mine in July and deliberately sit and idle to get as hot as possible. Passes with flying colors every time.
Click to expand...

Lucky you.
In AZ at 117degrees outside. it can be a different story.
I have everything upgraded for cooling and still struggling.. sitting still.
moving I am fine.
seeing 240-260 is too hot for my liking.
 
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