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  #1  
Old June 7th, 2020, 13:50
ljobbins ljobbins is offline
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Ca smog fail. Help!

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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  #2  
Old June 7th, 2020, 17:52
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blu3fan blu3fan is offline
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Re: Ca smog fail. Help!

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.
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Old June 7th, 2020, 17:56
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blu3fan blu3fan is offline
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Re: Ca smog fail. Help!

Other than that. low fuel pressure ?
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  #4  
Old June 7th, 2020, 18:09
ljobbins ljobbins is offline
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Ca smog fail. Help!

Quote:
Originally Posted by blu3fan View Post
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.

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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  #5  
Old June 7th, 2020, 18:16
lawsoncl lawsoncl is offline
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Re: Ca smog fail. Help!

Quote:
Originally Posted by blu3fan View Post
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.

How? You moving the crank sensor?
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  #6  
Old June 7th, 2020, 19:16
Black1990jeep Black1990jeep is offline
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Re: Ca smog fail. Help!

No egr valve? egr valve is a major factor in NOx smog.
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Old June 7th, 2020, 19:49
my2monkeys my2monkeys is offline
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Re: Ca smog fail. Help!

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,
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Old June 7th, 2020, 19:51
my2monkeys my2monkeys is offline
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Re: Ca smog fail. Help!

what did you fix that made it pass the functional test the 2nd time?
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  #9  
Old June 7th, 2020, 21:10
ljobbins ljobbins is offline
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Re: Ca smog fail. Help!

Quote:
Originally Posted by my2monkeys View Post
what did you fix that made it pass the functional test the 2nd time?
The pressure test?
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  #10  
Old June 7th, 2020, 21:12
ljobbins ljobbins is offline
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Re: Ca smog fail. Help!

Quote:
Originally Posted by Black1990jeep View Post
No egr valve? egr valve is a major factor in NOx smog.
Thanks but no egr in this engine. 1995
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  #11  
Old June 7th, 2020, 21:14
ljobbins ljobbins is offline
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Re: Ca smog fail. Help!

Quote:
Originally Posted by my2monkeys View Post
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,
Ive always been worried of this clogging up the cat if there is a lot of carbon. Am I wrong?
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  #12  
Old June 8th, 2020, 06:11
Black1990jeep Black1990jeep is offline
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Re: Ca smog fail. Help!

here is some info, 4.0 l jeep specific......

https://www.motor.com/magazine-summa...eptember-2005/
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  #13  
Old June 8th, 2020, 08:37
Black1990jeep Black1990jeep is offline
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Re: Ca smog fail. Help!

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.
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Old June 8th, 2020, 09:09
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Re: Ca smog fail. Help!

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.
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  #15  
Old June 8th, 2020, 11:00
ljobbins ljobbins is offline
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Re: Ca smog fail. Help!

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.
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