Failed CA Smog weird results.

[Mark1490]

This may not be weird but I have never seen it. I failed smog at 15mph but passed at 25. The only thing I know for sure may have not helped is I only had 20 psi in the tires and hear that can make a difference but don't want to take it back down there with just more air in the tires without getting a little feed back on my situation first.
Here are the results.
15 MPH NO (PPM) Max 517 Ave 28 Measure 674
25 MPH NO (PPM) Max 770 Ave 25 Measure 628
Any feed back is appreciated.

 

[souske]

Year/engine/trans are always useful bits of info for questions like this.

 

[Mark1490]

2001
4.0
AT not sure which on but it is a Cherokee Classic

 

[Gary Briggs]

I had a similar problem, high NOX is a result of excessive combustion temps, I ran a 180 thermostat and 2 heat range cooler plugs to pass.

 

[Mark1490]

So the smog tech said something about a miss but when I asked him more he said to go to ask a smog repair shop as he was only a star smog check place. Do you think that would have anything to do with the engine temp?

 

[Gary Briggs]

Re: Failed CA Smog weird results

The only thing I know is Smog "tech" guys don't know shit, they are most definitely not mechanics, and their advise should be researched thoroughly before implemented.

When I was having trouble passing they insisted it was a sensor problem, and I solved my issue with some spark plugs and a thermostat for about 15$

 

[Mark1490]

How would I know which plugs are a lower heat range plug?

 

[scottmcneal]

Did you have it tested in Indio? Little shop behind a used car lot, if you did i hope you walked next door to ask cause he knows what he is talking about.I have him do all my smog.He is about a mile or two pass the split.

 

[Mark1490]

I didn't I moved to Long Beach last year and went to a local place down here.

 

[scottmcneal]

OK, sorry. I noticed your location was Bermuda dunes.

 

[Gary Briggs]

2 heat range cooler, I only run these during the test, then I take them out and reinstall the NGK plugs I normally run

 

[Mark1490]

Thanks

 

[Hellbent]

that NOx is pretty high.
on the dyno test running 20 psi is going to create a pretty good load-which could create high combustion chamber temps.
you may pass by doing nothing more than airing up to 35-ish.
I had NOx issues a month or so ago during test time(around 1000ppm). colder plugs did practically nothing in my case. a new cat took me down to single digit NOx numbers.

 

[CompleteCherokee]

WHAT EACH SECTION IS
HC: Unburned Gasoline
CO: Partially Burned Gasoline
CO2: Completely Burned Gasoline
O2: Oxygen, the Good Stuff
NOx: Oxides of Nitrogen (This is only seen by a 5-gas smog machine)

WHAT THIS MEANS ON YOUR RIG
HC: misfire or bad burn
CO: too rich
CO2: engine efficiency
O2: too lean or just air
NOx: too hot or too lean

When I go get tested, I make sure to drive around for a solid 20-30 minutes to get the rig to operating temp, and I use a tank of high test before and during the tests. Make sure to bring it in immediately after the long drive so that its all still warm. What is your timing currently set at?

 

[cruiser54]

Ever tuned it up with plugs, wires, cap and rotor?

Due every 30,000 miles.....

Ryan's post^^ points to that.

 

[Mark1490]

It's an 01 so only thing to replace is the plugs. The timing is preset from the factory so that shouldn't be it ether.

 

[cruiser54]

It's an 01 so only thing to replace is the plugs. The timing is preset from the factory so that shouldn't be it ether.

When were the plugs replaced last and what brand?

 

[Mark1490]

Plug were about 10,000 miles and they are champions

 

[cruiser54]

NGKs are specified for the 2000 and 2001.

I've had crappy luck with Champions even when I worked at the Jeep dealer.

I'm wondering about the misfire....plug or injector? No CEL?

For sure I would run a can of BG44K through it. Add to a full tank. Run down to half tank. Fill again and run to 1/4 tank.

 

[Mark1490]

Well I put air in the tires and went with the cooler plugs and still failed.
Results:
NO (PPM) 15 mph MAX 517 AVG 28 MEAS 615
NO (PPM) 25 mph MAX 770 AVG 25 MEAS 616
Anymore suggestions would be great.