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Can't pass emissions

S

setht303

NAXJA Forum User
Location
colorado
Hey guys, my bro bought an 88 Cherokee and cannot pass emissions. It's registering high hc and nox. Any suggestions how to fix?
 
not a lot to go on there, but I'd look for sources of rich exhaust. Cylinder misfires, weak or insufficient spark, leaky injector, etc.

any of those will create high HC levels in the exhaust and the richer mixture will reduce the combustion chamber temperature, promoting the creation of oxides of nitrogen.
 
If you haven't resolved it by now, please post the actual results from the test.
 
Just in general...

When was the last time you replaced the O2 sensor? Coolant Temp Sensor?
These will both futz with the air/fuel ratio.

Are your vacuum lines all in good shape, connected, not cracked?
Grommets on the VC?
Full electric parts tune-up? Wires, cap, rotor, plugs?
Cat converter?

The RENIX emissions system is simple (only 1 O2 sensor) but sensitive and you're not going to get a CEL to tell you what's wrong. The best that you can do for your Jeep is to keep it maintained.

Check all of above and replace/repair as necessary...you'll get better mileage too.

...and read this if you haven't already

http://www.lunghd.com/Tech_Articles/Engine/Basic_Sensors_Diagnostics.htm
 
On a renix, check the air charge sensor. You can measure it with a simple ohmmeter.
 
Shorty said:
not a lot to go on there, but I'd look for sources of rich exhaust. Cylinder misfires, weak or insufficient spark, leaky injector, etc.

any of those will create high HC levels in the exhaust and the richer mixture will reduce the combustion chamber temperature, promoting the creation of oxides of nitrogen.
Click to expand...

NOx is created by running hot not running cool.

The Renix, his is an 88 also has an EGR valve.

OP, we need the entire report data set, to help with diagnostics. Is the engine running rough or smooth? Rough needs a tune up, so check spark plugs, wires, rotor, cap...and then test the O2 sensor (google "Ecomike NAXJA, oxygen sensor testing") to see if it is running open loop or closed loop.

It may also need a new Catalytic converter.
 
Ecomike said:
NOx is created by running hot not running cool.
Click to expand...

caught that a day-or-so ago and hoped no one else saw it...... 'twas a few beers into the night when I typed that :looser:

a failing EGR valve will allow the combustion chamber temps to climb and that will result in NOx levels being increased-- but I'd still look for causes of Hc levels to be high first.
 
Last edited:
Shorty said:
caught that a day-or-so ago and hoped no one else saw it...... 'twas a few beers into the night when I typed that :looser:

a failing EGR valve will allow the combustion chamber temps to climb and that will result in NOx levels being increased-- but I'd still look for causes of Hc levels to be high first.
Click to expand...


LOL, I wouldn't know about that, I never pisted tipos before, LOL!:laugh3:
 
Shorty said:
caught that a day-or-so ago and hoped no one else saw it...... 'twas a few beers into the night when I typed that :looser:

a failing EGR valve will allow the combustion chamber temps to climb and that will result in NOx levels being increased-- but I'd still look for causes of Hc levels to be high first.
Click to expand...

With me it's either not enough coffee in the morning or too many beers in the evening.
 
Nox check EGR valve, port/tube and perhaps a worn or degraded Catayltic converter too.

HC is unburnt fuel or incomplete combustion depending on PPM. Normal stuff tune up secondary ignition parts, CCV, PCV, timing both ign/mechanical (tchain). Fuel injectors.
 
cruiser54 said:
Probably true here, too. I get kinda cocky in the evening, too.
Click to expand...

So is there a proportional relation between high NOx and high HCs, and the intake of coffee or beer? Is there a time of day relationship?

LOL
 
Do you have fresh fuel in the tank or fuel that is a couple of months old?
Old engineoil?

I had problems with my jeep not passing emissonstest last year due to bad gas.
This year i made sure that the old fuel was out of the tank and then i filled it up with 15 liters of 99oktane fuel (V-power here in sweden) and did an oilchange. I drove it hard on the way to make sure that everything was at its working temperature.

The result:
The technican wondered what i had done to it because i got 0 on everything. (Exept the oxygensensor that has to bee between 0.97 and 1.03. mine was 1.00)
 
Damn I hate smog man its bull but has to be done. I do have the same problem. I gave in and sent it into the the shop a few days back. I did do a few things though before in high hopes that I could do it myself. I did full tune up chaged sparke plugs rotor cap all wire. Oil. Change. Sea foam repolaced both sensors after that. But in the end still didn't pass I gave in and sent it to get looked at. I had high nox due to a bad catlytic converter and he said few other things that I can't remeber at the moment. But if I were you just get a tune up and a new cat and get premium gas and run it through like the prevouis guy said it does help also fuel additives if you don't get premium gas. I hope to get mine back within a few days
 
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