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Unread 11-14-2013, 01:13 PM   #1
TonyMontana
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95 4.0 ZJ fails VA emissions due to high NO PPM

So I have a 95 ZJ with the 4.0 engine that's having issues passing emissions testing in the state of Virginia. I had replaced the catalytic converter because it had previously failed the emission test about a month ago. I got the Walker Cat that's advertised to be a direct fit at Advance Auto parts.

Fast forward to today, and I failed the emissions because of a high NO ppm reading that's almost more than double of what is allowed. The techs that did the emission were not helpful at all at telling me what it is and told me to pay $100 to diagnose it (typical Virginia bull****)

So now I'm here... wondering what can I do to lower the NO ppm?

I've attached the readings from the paper that I was given. What gets me is that my HC and CO% is pretty low yet the NO ppm is out of wack. IDK what this is an indication of.

All help is appreciated

Here's the attachments

dsc_0266.jpg

dsc_0267.jpg

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Unread 11-14-2013, 01:27 PM   #2
JohnCrabtree
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That's normal to charge to diagnose it. You paid them to do a smog CHECK. I don't see why you're angry that the techs did not want to work for free.

As for the smog stuff, I'm no help.
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Unread 11-14-2013, 01:45 PM   #3
TonyMontana
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Quote:
Originally Posted by JohnCrabtree View Post
That's normal to charge to diagnose it. You paid them to do a smog CHECK. I don't see why you're angry that the techs did not want to work for free.

As for the smog stuff, I'm no help.
Not angry at all about it... annoyed - of course, considering the fact that the state mandates this assery only in certain counties, and I had registered the car in such county. Then there's the fact that they want to charge me $100 to tell me "it MIGHT be (insert crazy idea that truly isnt)". I don't mind paying for a tech to diagnose, but if I'm going to spend $100 on a 18 year old Jeep then I expect it to be "Sir, this IS the problem, it will pass WHEN you fix this".

I should probably explain the fact that my other car is a Cutlass Supreme which no tech in the state of Virginia - more specifically the northern portion of it cannot diagnose anything on it. I've spent the car's worth in value on the "diagnostic" fee only to be told "durrrr i no no". My favorite one that I got from a tech was "What's an Oldsmobile?".

My point really is that this state has very incompetent people working as "techs" and they charge whatever they can for nothing. That's what irritates me the most. I've had to drive as far out as Baltimore, MD to get my cars fixed before... that's how bad techs are in my area.

So back on point... how can I lower my NO ppm, or "NOx" as some people call it.
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Unread 11-14-2013, 04:33 PM   #4
kensnelling
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Tony, there are some common problems and solutions, don't know if any of these are the cause of your problem.

Carbon buildup in the combustion chambers.
Sludge buildup in the crankcase due to infrequent oil changes.
Vacuum leaks.
A poor state of tune (old plugs, weak plug wires).

Do a google search and you will find several suggestions for causes and corrections, there are even special "snake oils" that you can use that are supposed to correct the problem.

Good luck

Ken
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Unread 11-14-2013, 05:24 PM   #5
Candymancan
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Weird anytime I have brought my 4.0 and my 5.9 in for emissions testing the guy only checks my computer for codes and my gas cap but my emission numbers like CO% and NO ect ect.. like on your papers.. always say N/A N/A N/A lol I brought my 5.9 in just recently and against they didn't even check my actuall emission numbers... just the gas cap and again and the codes...

And I live in virginia
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Unread 11-14-2013, 06:29 PM   #6
970001zj
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replace o2 sensors

also

high no levels are from the cat working too well :P
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Unread 11-14-2013, 07:51 PM   #7
TonyMontana
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Quote:
Originally Posted by Candymancan View Post
Weird anytime I have brought my 4.0 and my 5.9 in for emissions testing the guy only checks my computer for codes and my gas cap but my emission numbers like CO% and NO ect ect.. like on your papers.. always say N/A N/A N/A lol I brought my 5.9 in just recently and against they didn't even check my actuall emission numbers... just the gas cap and again and the codes...

And I live in virginia
Any car before 1996 gets dynoed. My 1994 Cutlass Supreme is the same thing. They don't connect it to the computer, they dyno it and give me the numbers. If your ZJ is a 1997 as your profile says, then that's why you get the "N/A" fields. The dyno is only for cars without the ODB2 computer, which my 95 is a car without.

Quote:
Originally Posted by 970001zj View Post
replace o2 sensors

also

high no levels are from the cat working too well :P
I'll check out the O2 sensors. Is it really possible for the new cat to put out high NO levels? The station was making commentary about the fact that I had a new cat before testing.

Also, I should probably add that the station I went to actually put the car on a dyno. They didn't put the sniffer in the tailpipe as other stations do. I don't know if that makes a difference in the NO PPM
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Unread 11-14-2013, 08:20 PM   #8
xcaliber81
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Did you get a performance readout lol.
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Unread 11-14-2013, 08:23 PM   #9
Candymancan
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Quote:
Originally Posted by TonyMontana View Post
Any car before 1996 gets dynoed. My 1994 Cutlass Supreme is the same thing. They don't connect it to the computer, they dyno it and give me the numbers. If your ZJ is a 1997 as your profile says, then that's why you get the "N/A" fields. The dyno is only for cars without the ODB2 computer, which my 95 is a car without.



I'll check out the O2 sensors. Is it really possible for the new cat to put out high NO levels? The station was making commentary about the fact that I had a new cat before testing.

Also, I should probably add that the station I went to actually put the car on a dyno. They didn't put the sniffer in the tailpipe as other stations do. I don't know if that makes a difference in the NO PPM
Mine are 98's but I didn't know that... I guess that sucks for you preOBD2 vehicles..
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Unread 11-14-2013, 08:31 PM   #10
xcaliber81
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Quote:
Originally Posted by Candymancan View Post
Mine are 98's but I didn't know that... I guess that sucks for you preOBD2 vehicles..
I dont have emissions testing so no worries here.
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Unread 11-14-2013, 08:36 PM   #11
Bullwinkle_98ZJ
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What type of EGR system does the 95 4.0L have?
Inspect the connections and ports closely. An EGR is closed at idle and open during higher RPM.

Try to SEAFOAM the engine.

Don't forget vacuum leaks.

Good luck.
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Unread 11-15-2013, 01:54 PM   #12
zjosh93
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No EGR on the 4.0. High NO is usually too high combustion temps. Can be lean mix, high compression, or too advanced timing. The cat should clean it up though. A cat working "too well" won't cause high NO. Modern catalyst substrate is design to catalyze both the unburned hydrocarbons and oxides of nitrogen. Was your Jeep warm when you had it dynoed? The cat needs to be hot to work properly. I've seen a few people go from fail to pass just by driving ten miles out and back on the highway before getting checked. Also you can look into the "Guaranteed to Pass" chemical treatment. Net lore says they don't do crap for hydrocarbons but they work alright for NO. Other than that a good ignition tune and some Seafoam to clean up the combustion chambers is a good start.
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Unread 11-17-2013, 02:15 AM   #13
TonyMontana
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Quote:
Originally Posted by xcaliber81 View Post
Did you get a performance readout lol.
The pics in the first post are the performance readouts... that's how I know I have a high NO PPM

Quote:
Originally Posted by zjosh93 View Post
No EGR on the 4.0. High NO is usually too high combustion temps. Can be lean mix, high compression, or too advanced timing. The cat should clean it up though. A cat working "too well" won't cause high NO. Modern catalyst substrate is design to catalyze both the unburned hydrocarbons and oxides of nitrogen. Was your Jeep warm when you had it dynoed? The cat needs to be hot to work properly. I've seen a few people go from fail to pass just by driving ten miles out and back on the highway before getting checked. Also you can look into the "Guaranteed to Pass" chemical treatment. Net lore says they don't do crap for hydrocarbons but they work alright for NO. Other than that a good ignition tune and some Seafoam to clean up the combustion chambers is a good start.
I'm leaning towards the lean mix and perhaps a vacuum leak as I noticed one of the tubes on the valve cover that go to the air box is broken.

The reason I'm leaning towards the lean mix is that the car feels a bit sluggish at times, most noticeable when the car is at a dead stop and i floor it. While on this topic, how can I retard/adjust the timing? I've read up a lot on people doing that to cars in order to pass the emissions, but not sure how.

I drove the car for 20 miles before taking it to the station, and I had even launched it a couple times in order to really work the engine. I was told once that the best thing to do is drive it 50 miles beforehand, but I think that's a bit much.

Anyways, easiest way to adjust the timing?
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Unread 11-17-2013, 09:17 AM   #14
PolkaPower
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So you can visibly see that you have a vacuum line broken and you have not fixed it?
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Unread 11-17-2013, 09:24 AM   #15
dnuccio
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Quote:
Originally Posted by TonyMontana View Post



The reason I'm leaning towards the lean mix is that the car feels a bit sluggish at times, most noticeable when the car is at a dead stop and i floor it. While on this topic, how can I retard/adjust the timing? I've read up a lot on people doing that to cars in order to pass the emissions, but not sure how.


Anyways, easiest way to adjust the timing?
you cant. ignition timing is set by the PCM. doesnt work like the old days where you can turn the distributer.
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